Documentation

Helpful Information to Configure Setting and Troubleshoot Issues

Documentation

Raptor Documentation

Table of Contents

Raptor Email Security End User Guide

Raptor Email Security only blocks email where we can be certain that the email is Spam or malicious. Otherwise, the email will be scored by our system and the subject changed for Spam. 

Many competitors use techniques that delay mail flow and incorrectly block legitimate emails. PCCC is a vocal opponent of these techniques.

How do I find an email is missing from my Inbox?

We take missing email very seriously. First, please check your Spam and Junk folders. If you still don’t find the missing email, please email support@pccc.com with the sender’s email address, the subject and the date/time. We will perform a log review.

How do I get rid of Spam in my Inbox?

Using Raptor is the first step! If the subject has Spam in it, then Raptor is working correctly. You can use rules to move these to other folders.

If you receive emails that ARE Spam but are not marked as Spam, please see the instructions below to submit these to PCCC for review.

How do I fix it when there is an email incorrectly marked as Spam?

These emails are called False Positives (FPs). Please see the instructions below to submit these to PCCC for review.

How do I send PCCC an email for Review?

The best way to submit an email for review is to create a new email message and drag the email to review over to the new email message as an attachment.

IMPORTANT: To make sure we get your email and it isn’t filtered, you will need to email the sample to a special address. Please email support@pccc.com or call (703) 359-9700 to receive the email address for submissions.

How do I Allow or Block a Specific Email?

Raptor Email Security is fully managed. By submitting emails for review and emailing our support, PCCC will make all the necessary configuration and algorithmic changes needed to block the bad email while keeping good mail flowing.

Why do my emails say [New], [Spam], [External], [Phish], etc. in the Subject?

Raptor Email Security uses these tags to convey important information about the email. The [Spam] or the older *****SPAM***** tags means Raptor identified the email as spam. The [External] means the email came from external. The [Phish] tag means that there is a high potential this is a phishing attempt or someone with a similar name at your firm. [New] means that this is a new email address that is contacting you. Used in combination, these tags can help greatly to keep your email safe and secure!

Raptor Email Security Admin User Guide

The following information has been prepared for System Administrators.

     Raptor Headers & Rules:

Raptor does not delete Spam emails but rather scores and tags them. If your users don’t want to see these emails in their Inbox, most email clients can use rules to move the Spam to a folder.

There are two Raptor headers that will be of interest: X-Spam-Status: & X-Spam-Level.

X-Spam-Status will include a Yes or No if Raptor marked it as Spam along with the total hits, the required score, and all the Raptor rules & subrules.

X-Spam-Level: will contain an asterisk for every integer in the email’s Raptor score. For example, a score of 5.99 would have a header of X-Spam-Level: *****.

The X-Spam-Level header is useful with rules to organize your email into folders. PCCC recommends rules to move Spam scoring below 15 into a folder named SPAM and Spam scoring 15 and over into a folder named SPAM15 The spam scoring over 15 will rarely contain incorrectly tagged emails.

If you use Microsoft Outlook, click here for instructions. If you use Mozilla Thunderbird, click here for instructions. If you use IMAP on PCCC’s cPanel infrastructure and would like rules added on the server for all of your users, please email support@pccc.com. NOTE: The process for creating rules is usually very straightforward and available in any modern mail client.

     Raptor Configuration

Raptor Email Security administrators can access https://Raptor.PCCC.com where you can do the following for your organization:

  • View Spam Statistics
  • Manage Raptor Continuity
  • Set a company-wide Auto-Responder
  • Block or Allow emails by Subject, Sender or Recipient
  • View Billing Information
  • Manage Raptor FAST Submissions

Raptor is designed around algorithms that are continuously improved and maintained by PCCC. You should NOT typically need to enter many entries into the welcomelists or blocklists. One exception to this rule is mailing lists and newsletters.

IMPORTANT: Raptor Email Security is fully managed. We recommend that you instruct your users to submit emails for review and email our support. PCCC will make all the necessary configuration and algorithmic changes needed to block the bad email while keeping good mail flowing to save you time for other administrative duties.

Notice for Managed Service Providers

The following information has been prepared for Managed Service Providers (MSPs). 

Raptor Email Security MSPs can access https://Raptor.PCCC.com where you can view your overall billing information as well as easily impersonate the administrator of any of the organizations under your management

Raptor Continuity End User Guide

User Guide

  1. Obtain your continuity password and login URL from your administrator.
  2. Log in with your email address and the provided password at the login URL.
  3. Optionally, you may also setup a desktop mail client. (Steps Detailed below)

Setting up Continuity IMAP

Thunderbird
  1. Request your continuity password and mail server information from your Administrator.
  2. Go to File -> New -> Existing Email Account
  3. Enter your email address and continuity password then click Continue.
  4. Click Manual config.
  5. Change the server settings to those provided by your Administrator.
  6. Change the username to be your complete email address.
  7. Click Re-test.
  8. Click Advanced config.
  9. Click Outgoing Server (SMTP).
  10. Select the row that lists your username as your full email address and click Edit.
  11. Change the Authentication Method to No authentication.
  12. Click OK.
  13. Click OK.
Outlook
  1. Request your continuity password and mail server information from your Administrator.
  2. Go to File -> Add Account.
  3. Select Manually Configure and click Next.
  4. Select Internet E-Mail and click Next.
  5. Enter your name and email address.
  6. SELECT IMAP account type.
  7. Enter the server settings provided by your Administrator.
  8. Enter your full email address as the username and your continuity password.
  9. Click OK, then Next.

Raptor Continuity Admin User Guide

  1. Using raptor.pccc.com, enter your domain and click Next.
  2. Login to the Raptor Customer Dashboard with your Raptor Customer Admin credentials.
  3. In the top or bottom ribbon under Raptor Continuity, select the Raptor Continuity Management option in the drop-down menu.
  4. Decide if you want to mass generate credentials or set them per account
    1. If you want to mass generate credentials, click the Generate Continuity Credentials button. (This will only add a password if the account has no continuity password already set.)
    2. If you want to set the credentials per account:
      1. click Edit on the account you want to set credentials for.
      2. Type the new Continuity password into the box.
      3. To save the new password click Edit Account.
  5. Provide the users with the accounts credentials and the link to login to the Raptor Continuity Portal.
    1. The link can be copied from the address bar if you click the Raptor Continuity option in the ribbon.
    2. The username is the full email address of the user.
  6. When the outage ends, you can instruct your customers that they can return to using their normal email client.

Attachment Help

HELP! I received a notice that my email was altered and an attachment was removed.

  1. The email was received but an attachment or multiple attachments were stripped because of the attachment’s extension. Click here to view a list of blocked attachments.
  2. This behavior is by design. PCCC’s Raptor Anti-Spam / Anti-Malware system DOES block many attachments based on extension because of their predilection for exploits.
  3. The extensions we block are carefully chosen to prevent malware spreading.
  4. If you are working with a known sender or recipient, a simple way to allow the email to go through with attachments is to change the extension to .RENAME. The system will allow the email through and the recipient can just rename it to use the file.
  5. We handle quarantine retrievals as noted in the email very quickly. If you need an attachment retrieved even quicker, don’t hesitate to pick up the phone and call us!
  6. We filter millions and millions of emails but generally only receive a handful of quarantine retrieval requests per month. Even so, we routinely see users request attachments from quarantine that are in fact new viruses not yet picked up by virus scanners. Our manual intervention is purposeful to prevent this from harming our customers or their e-mail recipients!

In conclusion, we know stripping attachments is annoying but it is done as part of our job to protect email from spam and malware!

Attachment Sizes

The max email size we allow is 35MB (35882577 bytes).  15MB is usually a good limit for Attachments to make sure it has a high deliverability rate.  25MB inbound is usually very safe. Note that attachments sent via e-mail are larger than they are on a hard drive. On a hard drive, files are usually in binary or 8 bit format. However, e-mails are in a 7 bit format. The conversion that occurs increases the size of attachments, often by 30%. Keep in mind that it’s the size of an e-mail that matters, not the attachment.

The largest e-mail that can be sent depends on the size limit of both the sender’s e-mail server and the recipient’s server. Most size limits are around 10 MB. Keep in mind that the size of an attachment is limited to the lowest limit in the chain of servers. Even if you have a 1 GB limit, if the other server has a 1 MB limit, the maximum size of the attachment is 1 MB. Also, note that attachments are larger than the original file due to conversion from 8 bit to 7 bit.

http://www.answers.com/topic/binary-and-text-files
http://en.wikipedia.org/wiki/Email_attachment

Attachment Retrieval 

To request retrieval of an attachment quarrantined by the Raptor, please contact PCCC by email at pccc-dot-com@pccc.com, referencing your message’s Quarantine Directory and SMTP Queue ID within 60 days.

Retrieval requests are typically completed within one business day.

Blocked Attachments

The following is a list of the file extensions which are blocked by Raptor Anti-Spam to help protect your computer from malicious attachments.

Dropped Files

Due to the likelihood of being malware, attachments with the following extensions are blocked entirely by Raptor by silently dropping the entire message, including files containing a class ID extension:

Extension DescriptionThreat
pifMS-DOS shortcutCan launch malware
comExecutable fileCan launch malware
scrScreen Saver ScriptCan launch malware
batExecutable batch fileCan launch malware
{*}class ID extensionClass IDs function the same way other extensions do, but without it being obvious what type of file is being used, and is commonly used to trick users into opening malware

Quarantined Files

The files below are quarantined and removed from the email. The original message with a note about the removed attachment will still be received, and the file can be retreived from the quarrantine by contacting PCCC. Click here for more help with attachments and retrieval instructions.

xllMicrosoft Windows ExecutablesCan launch malware or cause unexpected behavior

Extension Description  Threat
7z7z compressed file7z compressed files can contain autoexecuting exploits
adeMS Access project extensionAccess project files Can contain autoexecuting macros
adpMS Access project descriptionMacros
appMicrosoft FoxPro application / OS X binaryExecutables may launch malware
asdMicrosoft Office automatic backup fileMacros
asfStreaming videoBuffer overflow
asxStreaming videoBuffer overflow
basBASIC source fileCode execution can launch malware
chmCompiled HTML help fileExploits a buffer overflow found in Internet Explorer.
cmdExecutable batch fileCan launch malware
cplControl panel extensionCan launch malware
crtSecurity certificateCan override SSL certificates and lead to Man-in-the-middle attacks
dllDynamic Link LibraryCan launch malware
exeExecutable fileCan launch malware
exObfuscated form of exeCan launch malware
exeeObfuscated form of exeCan launch malware
ex_Obfuscated form of exeCan launch malware
fxpMicrosoft FoxPro executableCan launch malware
hlpWindows compiled help fileMacros
htaHTML application(Java)script can launch malware
gzCompressed archiveCompressed archive file format used to hide malware
imgImg ISO images became popular for DVDsSome OSes will mount img ISO images as drives allowing for malicious software installation
infSetup informationSetup scripts can be changed to do unexpected things
iniContains program optionsProgram options can be accidentally installed and cause programs to do unexpected or malicious things
insInternet Naming ServiceDNS hijacking/DNSChanger attacks
isoISO images became popular for CDsSome OSes will mount ISO images as drives allowing for malicious software installation
ispInternet SettingsDNS hijacking/DNSChanger, MITM attacks
jarExecutable Java fileCan launch malware
jsJavascript source fileCan launch malware
jseJavascript executableCan launch malware
libSoftware libraryIn theory, these files could be infected but to date no LIB-file virus has been identified
lnkWindows shortcutCan execute arbitrary code and run malware. Some people may accidentally attach a shortcut instead of the softlinked file
lzhCompressed archiveCompressed archive file format used to hide malware
mdbMicrosoft Access FileMacros can launch malware
mdeMicrosoft Access databaseMacros can launch malware
mimMIME-encoded fileBlocked due to an exploit in some versions of WinZip.
mscMicrosoft Common Console DocumentCan be changed to point to unexpected places.
msiWindows installer executableCan launch malware
mspMicrosoft Windows Installer PatchCan launch malware
mstMicrosoft Visual Test Source Files and SDK Setup fileSource can be changed to make your computer work unexpectedly
ocxObject Linking and Embedding (OLE) Control ExtensionCan launch malware.
pcdKodak proprietary photo CD imageCan launch malware.
prgFoxPro program source fileCan launch malware
rarRAR compressed fileCan lead to remote code exploits due to self-extracting archive capabilities
r00RAR partial archive compressed fileCan lead to remote code exploits due to self-extracting archive capabilities
regRegistry fileCan change system settings and cause unexpected behaviour
sctWindows Script ComponentCan launch malware
shUNIX shell scriptCan launch malware on UNIX workstations
shbShell Scrap Object FileCan launch malware
shsShell Scrap ObjectCan launch malware
sysSystem Device DriverCan launch malware, kernel level.
uueUUE archive fileCan be used to hide malware files
urlBookmarked URLFile with a web URL that can open nefarious
vbVisualBASIC runtimecan execute arbitrary code
vbeVisualBASICcan execute arbitrary code
vbsVisualBASIC scriptcan execute arbitrary code
vcsCalendar fileBuffer overflow in old Outlook versions
vxdVirtual Device DriverCan launch malware
wimWindows Image FormatCan launch malware
wmsWindows Media Player SkinCan launch malware
wscWindows Script ComponentCan launch malware
wsfWindows Script FileCan launch malware
wshWindows Scripting Host Settings FileCan launch malware or cause unexpected behavior
xllMicrosoft Windows ExecutablesCan launch malware

Conditionally Blocked Files

In addition to the above formats, some files are only blocked if certain conditions are met due to their widespread use.

ExtensionDescriptionConditions and Reason
zipFile ArchiveZIP archives contents are scanned using the same rules above. ZIP files which appear to be corrupted or in the wrong format (Files with a bad “magic file number”) are blocked, since they may contain exploits or executable malware.
emlEmail message attachmentEmail forwarded in this manner without being marked as multipart alternative are quarantined, since a client may inadvertently open this extension automatically and execute malware.

Disabled HTML Tags

In addition to scanning message attachments, Raptor will also scan HTML messages for potentially malicious content including the following:

TagReason
iframeIframe tags are used to “frame” or embed a remote website inside of an HTML email, and is blocked by Raptor due its use for phishing and tracking user email habits.
objectThe object tag is used to embed audio, video, ActiveX, PDF, Flash, and Java applets in an HTML document, which can be exploited on some clients to launch malware.
scriptThe script tag is used to embed a Javascript or other executable program into an HTML document, and can be exploited to launch malware.

Previously Blocked Files

Below is a list of files which were previously blocked by our spam filters, but since have been removed. Reasons for their removal from the block list may include the widespread prevalence of a certain format, and the use of better secured software by clients.

ExtensionRemoval  DateReason
rar2012-07-25RAR files have had exploit vectors but the prevalence of the file format is too high. Please make sure you are using recent and secure software to handle RAR files.
vcs2013-05-11Old versions of Outlook contained buffer overflows which could be exploited when importing a calendar. The prevalence of the format and use of clients that no longer suffer from this vulnerability has prompted the removal of this file block.

Explanation of Threats

Macros

Macros are executable extensions of specific programs which are designed to automate long and tedious tasks. While some macro languages are limited from a programming perspective, many try to extend their usefulness by calling outside programs. Since some programs, such as document processors and office suites, allow the embedding of macros, it is possible to construct a malicious document that would download and run more capable malware as soon as it was opened.

We work to score Office documents with macros so they are considered spam due to the risk in receiving them.

Malware

Malware is a general term used to describe malicious software which causes unwanted, intrusive operation of a computer, normally unknown to the user. Malicious software includes but is not limited to virusesadwaretrojansworms, and spyware. Common infection vectors for malware include email attachments, intentional or driveby downloads, and removable media such as thumbdrives.

Viruses
A computer virus is one type of malware which can spread by itself. As Wikipedia puts it, “the term “virus” is also commonly used, albeit erroneously, to refer to many different types of malware and adware programs.”

Adware

Adware is a type of software which displays or injects internet advertisments in an attempt to gain the author ad-revenue. Some adware may come from legitimate companies to support a business model, and may come bundled with your computer. Other sources may present unwanted pop-up ads, and generally are classified as having malicoius intent.

Trojans

A trojan, or “trojan horse”, is malware that masquerades as or is bundled with legitimate software. Sophisticated trojans, coupled with the implicit trust that a computer user unknowingly grants to the malware, is capable of cripling or disabling anti-virus software entirely, while consealing the problem from the user to evade detection.

Worms

A worm is a type of malware designed to replicate itself to spread to other computers or servers, usually relying on security flaws in physical networks to spread to as many computers as possible [1].

Spyware

Spyware is malware designed to silently steal information about an infected computer’s user by logging keystrokes, accessing local files, and collecting stored application data to be sent back to the spyware author. Some spyware is the direct payload of a trojan, although some has been known to spread as a virus.

Ransomware

Ransomware, sometimes known as cypherware, is a malicious program which encrypts personal documents stored on computers or otherwise restricts access to the computer, holding the computer “hostage” and demanding money in exchange for the decryption or access key. While some ransomware is trivial to defeat, the best defense against ransomeware is to keep recent backups of your all personal documents.

Buffer Overflow

A buffer overflow is an unintentional flaw in software which can be exploited to run malware with the same privledges as the exploited program. An old or outdated browser may contain known buffer overflow exploits, which can be exploited to run malware through a specially crafted website. Keeping all installed software up to date is important to preventing security issues from buffer overflows.

Outlook Spam Folder Rules

 

Microsoft Outlook Raptor Anti-Spam Rule Recommendations
The Raptor Anti-Spam / Anti-Malware system labels unwanted emails with “[Spam]” in the Subject header. Some users receive hundreds and thousands of these unwanted emails per day so filing them away becomes imperative. These instructions will help you make two rules to filter out these emails with Microsoft Outlook.

1. Create 2 Folders to hold Spam marked by Raptor: 1 folder for Spam below a score of 15, and 1 for Spam scoring 15 and over.

A. On your Inbox you will Right Click and select “New Folder”.

B. Create another Folder and name it SPAM15. (If Outlook 2019 created a “spam” folder, name this new folder “spam15” for consistency.)

2. Now go to the File tab.

3. Click on Rules and alerts.

4. Click on New Rule and start from a blank rule.

5. Select “Apply rule on messages I receive” and click Next.

6.Check the condition “with specific words in the message header”

 

7. Click on “specific words” link in Step 2.

8. Enter “X-SPAM-Level: ***************” without the quotes in the Search Text box.

9. Click Add

10. Click OK

11. Click Next and select “move it to the specified folder”.

12. Click on “specified” link in Step 2.

13. Choose the “SPAM15” folder.

14. Click OK.

15. Click Finish.

16. Click on New Rule and start another rule from a blank rule.

17. Select “Apply rule on messages I receive” and click Next.

18. Check the condition “with specific words in the subject”

19. Click on “specific words” link in Step 2.

20. Enter “[Spam]” without the quotes in the Search Text box.

21. Click Add.

22. Click OK.

23. Click Next and select “move it to the specified folder”.

24. Click on “specified” link in Step 2.

25. Choose the “SPAM” folder.

26. Click OK.

27. Click Finish.

28. It’s important that you run the SPAM 15 & Over Rule first. If you created the rules in a different order, use the up/down arrows to change the order of the rules.

29. Click Apply

Periodically, you should check these folders and delete the unwanted e-mails. Also, if an email is missing, you check these folders (and the Junk Email folder if you use Outlook’s Junk Email Filter) first.  Because a higher score indicates an email is more likely to be spam, you should not have to check the SPAM15 folder as often as the SPAM folder.

Thunderbird Spam Folder Rules

Mozilla Thunderbird Raptor Anti-Spam Rule Recommendations

The Raptor Anti-Spam / Anti-Malware system labels unwanted emails with “[Spam]” in the Subject header. Some users receive hundreds and thousands of these unwanted emails per day so filing them away becomes imperative. These instructions will help you make two rules to filter out these emails with Mozilla Thunderbird

  1. On your inbox, Right Click and select “New Folder”.
  2. Name the new folder Spam
  3. Create another folder named Spam15.
  4. Left Click on the email account name above Inbox.
  5. Select “Message Filters”.
  6. Click New… to start from a blank filter rule.

  7. Ensure Getting New Mail: is checked.

  8. Click the drop-down that by default states Subject and select Customize.

  9. In the pop-up box, enter X-Spam-Level.

  10. Click Add

  11. Click OK to close the pop-up and X-Spam-Level will now be selected.

  12. Enter “***************” without quotes in the right-most text box

  13. Under “Perform these actions:”, select “Choose Folder…”
  14. In the drop-down, select your email account, select Inbox and then choose the Spam15 folder
  15.  


15. After verifying the information click OK to add the new Filter Rule


16. Next, click on New and start another blank rule.

17. Ensure Getting New Mail: is checked.

18. Ensure the far left drop-down states Subject and in the right-most text box enter, “[Spam]”

19. Under “Perform these actions:”, select “Choose Folder…”

20. In the drop-down, select your email account, select Inbox and then choose the Spam folder


21. After verifying the information click OK to add the new Filter Rule

22. It’s important that the Spam15 Rule is first. If you create them in a different order, use the Move Up and Move Down options to change the order.

23. Periodically, you should check these folders and delete the unwanted emails.

If an email is missing, you should check these folders first.

Because a higher score indicates an e-mail is more likely to be spam, you should not have to check the Spam15 folder as often as the Spam folder.

No Reply Address Setup for cPanel

If you legitimately use addresses like noreply@ to send emails, you need to ensure that address exists.

If you use cPanel, the following will do so and limit the storage for the account to 1 MB.

  1. Login to your cPanel account at :2083 (For example: cpanel.pccc.com:2083)
  2. Under the Email section, click Email Accounts.
  3. Click Create.
  4. Select the domain that needs the new account.
  5. Enter noreply as the username.
  6. Setup a password that meets the requirements or autogenerate. (This account should rarely/never be logged into.)
  7. Click Edit Settings.
  8. Set 1 MB storage space.
  9. Under the Automatically Create Folders for Plus Addressing, select Do Not Automatically Create Folders.
  10. Create the account.
  11. Under the Email section on the main dash, click Forwarders.
  12. Click Add Forwarder.
  13. Enter noreply in the address line.
  14. Click Advanced Options to reveal more options.
  15. Select Discard then Add Forwarder.

NOTE: Add other aliases to this account as needed.

Email Compendium

This compendium is intended to be read by administrators as well as SpamAssassin users who want to learn more about e-mail and anti-spam. It is a living document and we welcome your comments and suggestions, which can be submitted by using the Report a Problem page.

What is E-mail?

E-mail is the amalgamation of many plain-text protocols, and other specifications, defining the structure of the body of an e-mail, associated header information, and how to send and receive e-mail. E-mail predates the internet and has a complicated history. E-mail as it is defined today is specified by a number of RFCs. Occasionally a new RFC will be published that includes minor refinements.

A basic example of sending an e-mail is below:

helo intel1.pccc.com - THIS IS THE "HELO"(aka "Hello") GREETING,
INITIATING DIALOG WITH THE MAIL SERVER BY
IDENTIFYING THE MACHINE YOU'RE USING.

mail from:
rcpt to:

data - THE MESSAGE FOLLOWS
Subject:
-- END THE HEADERS WITH AN EMPTY LINE

.       — INPUT A PERIOD, THIS “SENDS” THE MESSAGE
AT WHICH POINT THE SERVER WILL PROVIDE A DSN REGARDING YOUR SENT MESSAGE

quit – THIS ENDS THE SESSION WITH THE SMTP SERVER

 

After you send an e-mail any number of things can happen, depending on how your mail server is configured, who you are sending to, and even how many other people are sending e-mail as well.

In the very basic hypothetical example, you are on a Unix-like operating system sending a message from one user to another on the same machine. Because you are an old fogey, you open up mutt and send a message from yourself@localhost to root@localhost. It contains the message “[sudo] password for root:“. You submit the message to localhost, which then “sends” the message to itself. When localhost receives the message from itself, it places it in the root mailbox, ready for reading. The same process repeats when the root user replies with the message “hunter2“.

Servers that Handle E-mail

The typical handoff of e-mail between servers is described in detail on Wikipedia. There are a few major entities involved in the process of sending e-mail from one place to another. They are:

MUA – Mail User Agent or e-mail reader or e-mail client

Any agent acting as a client toward an e-mail server, regardless of it being a mail user agent, a relaying server, or a human typing on a terminal. In addition, a web application providing message management, composition, and reception functionality is sometimes considered an e-mail client.

An MUA is only active when a user runs it. Messages arrive on the Mail Transfer Agent (MTA) server. Unless the MUA has access to the server’s disk, messages are stored on a remote server and the MUA has to request them on behalf of the user.

As a basic function, an MUA is able to introduce new messages in the transport system. Typically, it does so by connecting to either an MSA or an MTA, two variations of the SMTP protocol. The client needs to put a message quickly without worrying about where the message eventually will be delivered: that’s why a transport system exists. Thus it always connects to the same preferred server, however, how does that server know that it should accept and relay submissions from that client?

There are a number of ways. One way is to recognizes the client’s IP address, e.g. because the client is on the same machine and uses internal address 127.0.0.1, or because the client’s IP address is controlled by the same internet service provider that provides both internet access and mail services.

Another way is to authenticate since the SMTP protocol has an authentication extension. The latter method eases modularity and nomadic computing but can cause e-mail passwords to be sent using a clear-text protocol.

Finally, there is a technique called POP Before SMTP that requires a user to check mail before sending e-mail that then records the IP address and allows relay for a temporary period of time.

Client settings require the name or IP address of the preferred outgoing mail server, the port number (25 for MTA, 587 for MSA), and the user name and password for the authentication, if any. It is also typically possible to use port 465 for SSL encrypted SMTP sessions (SMTPS) that many clients and servers support.

Transport Layer Security (TLS) encryption can be configured for the standard ports, if both the client and the server support it.

http://en.wikipedia.org/wiki/Mail_User_Agent

MSA – Mail Submission Agent

MSA is a software agent that receives electronic mail messages from a mail user agent (MUA) and cooperates with a mail transfer agent (MTA) for delivery of the mail. It uses a variant of the Simple Mail Transfer Protocol (SMTP), as specified in RFC 4409

RFC 4409 requires that clients are authorized and authenticated to use the mail submission service, e.g., as described in SMTP-AUTH, by other means such as RADIUS, or POP before SMTP. The MSA must check that the submitted mail is syntactically valid and conforms to the relevant site policies.

*

RFC 4409 contains some optional features:

Enforce submission rights guarantees that the envelope sender address is valid and authorized with the used authentication. This is in essence the SPF model specified in RFC 4408.

May add sender permits to add a Sender address header field if the envelope sender address does not match any author address in the “From” header field. This is roughly the Sender ID model specified in RFC 4406 – ignoring the tricky case of Resent-From header fields not covered in RFC 4409.

*

Many Internet service providers and enterprise or institutional networks restrict the ability to connect to remote MTAs on port 25 (the usual SMTP port). Availability of a Mail Submission Agent on port 587 enables nomadic users to continue to send mail via their preferred submission servers even from within others’ networks. Using a specific submission server is a requirement when sender policies are enforced.

Most of the benefits mentioned above may also apply to authenticated MTA, that is port 25 after the user logs in. In fact, the relevant server software is often the same for both services. However, the very fact that the service can be made available on a different port can be considered a further benefit, as it allows for circumvention of restrictions on port 25.

http://en.wikipedia.org/wiki/Mail_submission_agent
http://wiki.linuxquestions.org/wiki/Mail_submission_agent

MTA – Mail Transfer Agent or Mail Relay

A software agent that transfers electronic mail messages from one computer to another. An MTA implements both the client (sending) and server (receiving) portions of the Simple Mail Transfer Protocol (SMTP). There are many ways to configure an MTA. A few common ones are listed below.

http://en.wikipedia.org/wiki/Mail_transfer_agent

External Relays – An external relay basically allows two organizations to share the same domain name but at the same time separate e-mails between them. Basically, when the server of one organization receives an e-mail sent to the other organization, the server redirects the e-mail to the server of the other organization. So basically, say we have organization A and organization B in an external relay domain. If organization A gets an e-mail for organization B, A’s server gives it to B’s server.

http://technet.microsoft.com/en-us/library/bb124423.aspx

Internal Relays – In an internal relay domain, most recipients of e-mails don’t have mailboxes in a certain server organization. An organization may have to share SMTP address space with two or more e-mail systems. All users have the same domain suffix in their e-mail addresses. So, when someone is trying to send an e-mail to someone who isn’t in one e-mail system, instead of giving a non-delivery report, the server then tries to find the e-mail address that matches the address specified in the e-mail.

http://technet.microsoft.com/en-us/library/bb124423.aspx

Last External Relay – In an external relay domain, the last external relay is the last server that is outside your own network that relayed the e-mail to your own server. So basically, say we have organization A and organization B in an external relay domain. If organization A gets an e-mail for organization B, A’s server gives it to B’s server. A’s server is the last external relay. Look at the header of any e-mail. You should be able to find the last external relay.

SMTP Relay – Basically, a server is called an open relay, or SMTP relay, if it accepts messages on the behalf of other domains and doesn’t require authentication. A person in China could send a message through a server in South Africa to a person in California. As I hope you can see, this can easily be abused by spammers who send massive amounts of e-mails through an SMTP relay server without being discovered who they are.

http://www.xeams.com/smtprelay.htm

MDA – Mail Delivery Agent

Mail Delivery Agent is computer software that is responsible for delivering e-mail to a recipient’s mailbox.

Within the Internet mail architecture, the message delivery agents consist of two components, the message handling service side that accepts messages from the message transfer agent (MTA), and a component in the recipient’s environment that affects message storage in a mailbox or other customized mechanisms.

Usually, the mail delivery agent is not started independently but with the message transfer agent.

An example of an MDA is procmail on Unix systems. Procmail’s handling of e-mails can be heavily influenced through the use of procmailrc scripts.

Some message delivery agent software for Unix-like platforms

  • binmail (The MDA portion of Sendmail)
  • Delivermail
  • fdm
  • maildirproc
  • maildrop
  • postdrop
  • procmail
  • Courier-pop
  • Courier-imap
  • dovecot

http://en.wikipedia.org/wiki/Mail_delivery_agent

MX Records – Mail Exchanger Records

An MX Record is a record in the DNS that specifies a mail server responsible for accepting e-mail messages on behalf of a recipient’s domain and prioritizes mail delivery. It specifies how e-mail should be routed with SMTP.

Though the practice of pointing MX records to CNAME (alias) records is not that uncommon, it certainly isn’t in keeping with internet standards.

The domain name used as the value of an NS resource record, or part of the value of an MX resource record must not be an alias. Not only is the specification clear on this point, but using an alias in either of these positions neither works as well as might be hoped, nor well fulfills the ambition that may have led to this approach. This domain name must have as its value one or more address records. Currently those will be A records, however in the future other record types giving addressing information may be acceptable. It can also have other RRs, but never a CNAME RR.

Additional section processing does not include CNAME records, let alone the address records that may be associated with the canonical name derived from the alias. Thus, if an alias is used as the value of an NS or MX record, no address will be returned with the NS or MX value. This can cause extra queries, and extra network burden, on every query.

http://en.wikipedia.org/wiki/MX_record

SMTP Culpability

As e-mail moves from one server to the next, SMTP adds a header file marking the e-mail as having been passed along successfully, failed, or permanently failed. These headers help determine “SMTP Culpability” by showing which server along its way to its destination was responsible for a temporary or permanent failure.

From RFC2821 3.8.2 Received Lines in Gatewaying

When forwarding a message into or out of the Internet environment, a gateway MUST prepend a Received: line, but it MUST NOT alter in any way a Received: line that is already in the header.

“Received:” fields of messages originating from other environments may not conform exactly to this specification. However, the most important use of Received: lines is for debugging mail faults, and this debugging can be severely hampered by well-meaning gateways that try to “fix” a Received: line. As another consequence of trace fields arising in non-SMTP environments, receiving systems MUST NOT reject mail based on the format of a trace field and SHOULD be extremely robust in the light of unexpected information or formats in those fields.

The gateway SHOULD indicate the environment and protocol in the “via” clauses of Received field(s) that it supplies.

http://en.wikipedia.org/wiki/Simple_Mail_Transfer_Protocol

Attachments

Note that attachments sent via e-mail are larger than they are on a hard drive. On a hard drive, files are usually in binary or 8 bit format. However, e-mails are in a 7 bit format. The conversion that occurs increases the size of attachments, often by 30%. Keep in mind that it’s the size of an e-mail that matters, not the attachment.

The largest e-mail that can be sent depends on the size limit of both the sender’s e-mail server and the recipient’s server. Most size limits are around 10 MB. Keep in mind that the size of an attachment is limited to the lowest limit in the chain of servers. Even if you have a 1 GB limit, if the other server has a 1 MB limit, the maximum size of the attachment is 1 MB. Also, note that attachments are larger than the original file due to conversion from 8 bit to 7 bit.

http://www.answers.com/topic/binary-and-text-files
http://en.wikipedia.org/wiki/Email_attachment

What is Spam?

Many people try and use various legal definitions such as CAN-SPAM in the US. This definition clearly has problems for the global community of the internet. Spammers routinely fail to understand that the Internet is much larger than one country’s laws.

We find the definition of CONSENT to be best. It leaves the content of any e-mail in the eye of the beholder. In short, if you consent to receive e-mails about XYZ, then those e-mails are not spam by definition.

The name “spam” refers to a skit by Monty Python’s Flying Circus which involves an overload of unwanted items offered at a café all including SPAM. A patron who doesn’t like SPAM certainly won’t like “SPAM SPAM SPAM SPAM SPAM SPAM SPAM baked beans SPAM SPAM SPAM and SPAM”. Hence, an overload of unwanted items became known as spam (but not SPAM).

Hormel, naturally, defines SPAM as their spiced ham product. And the use of their trademark to refer to junk e-mail has necessitated their lawyers to come up with an entire position on the matter. To avoid confusion in this document, the Hormel trademark will always be written as “SPAM” in all-caps.

What isn’t Spam?

In the anti-Spam community, Spam and Ham are opposites. Spam refers to Junk E-mails and Ham refers to Good E-mails.

Since Ham is “Treif”, or non-kosher for those who follow Jewish dietary laws, some people have proposed using the word Yam, instead of Ham. We are firmly anti-vegetable and will not stand for such nonsense.

Who Sends Spam?

Spam is sent from all over the world. More and more seem to be sent by organized crime. Bot networks of infected computers often send massive amounts of spam.

Spammers often obtain e-mail addresses by using dictionary attacks. Basically, they send e-mails to lists of names. Unsubscribe links help verify that an e-mail address exists.

Spammers also use e-mail addresses posted publicly on websites. They also often employ malware to obtain address books off computers.

Spammers send spam to make money by selling something, to make money by stealing from you, and trick you into installing malware that lets spammers send even more spam, repeating the cycle.

What is SpamAssassin?

Apache SpamAssassin is a mail filter and programming interface that identifies junk e-mail. SpamAssassin at it’s heart is a Scoring Framework. This framework allows virtually any anti-Spam technologies to be added and used.

The engine for SpamAssassin is sometimes called a “Rules-Based Heuristics Engine” because the filter typically looks for patterns such as common phrases or known senders. Heuristics is the application of experience-based techniques for problem solving. Virus scanners use the same technique and are also heuristics engines. As an e-mail goes through the engine, each of the rules for SpamAssassin are run and generate a score. These individual scores are then totaled to provide an overall score for the e-mail. Some rules are positive and add to the score. Some rules are negative take away from the score.

The lower the overall score is, the more likely the e-mail is Ham. The higher the score, the more likely the e-mail is Spam.

But not each rule has the same weight. The weight each rule is given is determined first by initial “guesses” and later refined through optimization. We use a Genetic Algorithm to optimize the scores. Given a list of rules and a set of existing spam/ham classifications, SpamAssassin can automatically determine how best to weigh each rule. You can read more about Genetic Algorithms on Wikipedia. Discussing the finer details of Genetic Algorithms is outside the scope of this document.

Not everyone will want to use SpamAssassin to do the actual e-mail processing. With this design, you don’t have to use SpamAssassin to filter your mail.

Instead, you can also use SpamAssassin from other programs. In this way, SpamAssassin can be used to return a “this is spam/this is ham,” a score, a list of rules that lead to the score, and a detailed report. It’s then the job of the parent program that calls SpamAssassin to decide what to do with this information. Most e-mail clients using SpamAssassin have the ability to dispose of e-mails that SpamAssassin thinks is spam. Some clients, such as Thunderbird, have the ability to directly read the SpamAssassin scores and filter based on that.

If you are unsure why an e-mail was or was not tagged, make sure to first check the headers of the e-mail. Simple problems such as whitelisting of a Spammer are often at the root of the problem.

Also, check blacklists. If a blacklist lists a site and you want to delist it, follow the instructions! And NEVER pay any money for delisting.

Making Your Own Rules

Make sure to go to http://wiki.apache.org/spamassassin/WritingRules.

Remember these commands are for Unix-like environments.

Lint is a program that looks for bugs in source code. Make sure every rule you write passes lint without any problems by checking with the command “spamassassin -D –lint” Make sure to do this!

First, make sure the rules you write are not already implemented. If you want to change the rule, just change the default score.

Then, write your own rules! It is a good idea to score your rules low to prevent false positives. Make sure to write rules for your circumstances! For example, when writing a negative rule, pick tokens that commonly appear in ham e-mails addressed to you! Use phrases instead of single words.

Finally, test it! Make sure it passes Lint. Then, test it by running spamassassin in test mode against a text file containing the contents of an e-mail with:

spamassassin .t-D<[message]

Or without network tests:

spamassassin .t-L-D<[message]

‘-D’ prints out debug information.

When to Catch Spam

Spam can really be detected at any time. However, the later spam is identified, the more resources the server has used, and therefore the expenses rise. The rule of thumb is to reject early on. The various stages:

    • Connection
      The server decides if it wants to accept and forward the client’s connection attempt to the SMTP server
    • SMTP session
      The SMTP server examines data sent, e.g. client IP address, envelope sender, envelope recipient etc., in the SMTP session and decides if it wants to accept or reject the client, sender, recipient or message
    • Reputation
      The server consults an external (local and/or remote) system to query the reputation of the client or sender domain
    • Content
      A content filter examines SMTP session data and/or message content and decides if the message is spam or ham

For Apple OS X Users: Not Much Interface (You should still read this though)

As of Snow Leopard, the Apple OS X GUI provides very little interface and customization for the inner workings of Spam Assassin. The server preferences in Snow Leopard only allow for two options relating to Junk Mail:

  1. Enabling the filter
  2. Setting the threshold that is used to mark an e-mail as spam.

Even the mail service settings page shows only a few tweaks. The Accepted languages and locales option doesn’t even work for the included version of SpamAssassin!

Snow Leopard uses an extremely outdated version of SpamAssassin. 3.2.1, the version it uses, was released June 11th, 2007! 3.2.5 was released June 12th, 2008!

What You Need:

  1. Terminal: try to get familiar with it
  2. Vi: A must! It’s not easy but it is a very powerful and very fast text editor. It should exist on Unix-based boxes. Run the command vimtutor and follow the the tutorial.
  3. Xcode: As an administrator, you should have Apple’s Development Environment. It provides GNU compiler collection and other tools.

Tweaking

First, consider your threshold for tagging. A 6.0 to 7.0 score as a threshold is recommended. However, many use thresholds from 5.0 to 20.0. Remember, thresholds can be non integers such as 7.5.

Using network tests for SpamAssassin can significantly improve your Junk Mail filter. Some blacklists you can use (be careful about rules and limits):

To enable these, typically you add a few configuration lines or a *.cf file in the directory ‘/etc/mail/spamassassin’. Some are available in the default SpamAssassin rules, depending on the version of SpamAssassin. Make sure you don.t duplicate a blacklist by checking the headers in a few filtered e-mails!

Check that network tests are enabled in AMaViS, short for A Mail Virus Scanner, by editing /etc/amavisd.conf and checking the line for local tests reads ‘$sa_local_tests_only=0;’.

Checksum Filters are also available, albeit with more difficulty. Try these commands for more information: ‘perldoc Mail::SpamAssassin::Plugin::DCC’, ‘perldoc Mail::SpamAssassin::Plugin::Pyzor’ and ‘perldoc Mail::SpamAssassin::Plugin::Razor2’.

To make such network tests run faster, install a local caching nameserver. In OS X, turn on DNS in Server Admin and in System Preferences->Network, change your DNS resolution to the DNS server on your local host as the first DNS entry.

In SpamAssassin, the Bayesian Classifier learns tokens, words or short sequences that are commonly found in spam or ham. The command ‘sa-learn’ (also available in Unix) teaches the Bayesian Classifier new words or short sequences. In mail services that use SpamAssassin, a Junk Button is often included. This button interfaces with the command ‘sa-learn’.

The script that runs ‘sa-learn’ on the ham folder (notjunkmail) and the spam folder (junkmail) is located in /etc/mail/learn_junk_mail. To use this script, it is first required to create the e-mail accounts junkmail and notjunkmail. Then, redirect all spam that are reported as negative to the junkmail address and Ham that are reported as positive to the notjunkmail address. Using the Bayesian Classifier, SpamAssassin will learn from these e-mails. It is also possible to use SpamTrainer from http://osx.topicdesk.com/spamtrainer. Since new rules learned by the Bayesian Classifier will not be used until there are at least 200 tokens, SpamTrainer allows you to manually make SpamAssassin learn some folders of Spam and Ham. Once 200 tokens are found, you should see BAYES_* rules in e-mail headers and reports.

Look at the *.pre files and the *.cf files in /etc/mail/spamassassin/. The local.cf is your configuration file for SpamAssassin. It contains many more customizations than the GUI shows for SpamAssassin. Before making changes to any of these files, backup them with a new file just in case the GUI interfaces accidently changes something. You can manually blacklist and whitelist senders with certain entries, such as:

  • whitelist_from + e-mail address : whitelist the e-mail address(not recommended, because it also whitelists forged e-mail addresses).
  • whitelist_to + e-mail address: Disable SpamAssassin for a certain local user
  • use the command .man Mail::SpamAssassin::Conf. for more configuration options

Plugins are implemented in the *.pre files. Most are not implemented in default. For example, to use the TextCat plugin, edit the file /etc/mail/spamassassin/v310.pre and remove the # that is commenting .loadplugin Mail::SpamAssassin::Plugin::TextCat..

For Windows Users: Installing

SpamAssassin development for Windows has stalled over the past few years. However, you can still download a precompiled native Window version with similar capabilities at http://www.jam-software.com/spamassassin/index.shtml. However, please keep in mind that this version is extremely unstable and creates multiple memory leaks. You must have a Mail Transfer Agent (MTA) such as hMailServer or Exchange that can interface with SpamAssassin. If you want, you can also install the actual SpamAssassin using the following steps:

More in-depth:

http://www.jam-software.com/spamassassin/manual.php
http://wiki.apache.org/spamassassin/InstallingOnWindows

Installing : (per Daniel Lemke)

  1. Install or upgrade ActivePerl
    1. Download from www.activestate.com
    2. Download nmake from Microsoft at http://download.microsoft.com/download/vc15/Patch/1.52/W95/EN-US/Nmake15.exe
    3. Extract nmake.exe and nmake.err to your bin folder in perl.
      1. Use the command PPM to install required modules(first two) and the optional modules: ppm install Net-DNS
      2. ppm install NetAddr-IP
      3. ppm repo add tcool
      4. ppm install DB_File
      5. ppm install Mail-SPF
      6. ppm install IP-Country
      7. ppm install Net-Ident
      8. ppm install IO-Socket-INET6
      9. ppm install IO-Socket-SSL
      10. ppm install Encode-Detect
      11. ppm repo add bribes
      12. ppm install Mail-DKIM
  2. Install Microsoft Visual C++ 6.0 or later or another C compiler
  3. Download the SpamAssassin zip file from the official website
  4. Set the following the system environment variables:
    1. RES_NAMESERVERS=
    2. LANG=en_US
  5. Extract the zip file anywhere.
  6. Open up command prompt and switch the directory to the SpamAssassin directory
    1. Type perm makefile.pl
    2. nmake
    3. nmake test (optional)
    4. nmake install
  7. Make a test folder and create a sample-spam.txt file and a sample-nospam.txt in the site configuration folder ( C:\perl\site\etc\mail\spamassassin).
  8. Switch the directory to the site configuration folder
    1. Type sa-update .nogpgp
  9. Test the files!

Procmail Info

Procmail is a mail delivery agent (MDA) available on Unix-like environments that sorts incoming mail into specified directories and uses SpamAssassin to filter out spam. Procmail usually automatically runs all e-mails through SpamAssassin; however, it doesn’t automatically put these e-mails into a ‘spam’ directory. This requires a certain tweak:

Add this using any editor:
:0:
* ^X-Spam-Status: yes
$HOME/imap/spam

It would also be good to manually run the Bayesian Classifier(read more about this in the OS X section) by using the command ‘man sa-learn’ and setting ‘use_bayes 1’ in the ‘~/.spamassassin/user_prefs’ file.

http://ftp.ks.uiuc.edu/Development/Computers/docs/user/procmail.html

How to Catch Spam

Author Domain Signing Practices – ADSP is an optional extension to DKIM where a domain administrator can specify the DKIM signing practice. ADSP is an additional DNS record that is used alongside DKIM. With ADSP, an organization can specify one of three DKIM signing practices. Unknown is the same as not having an ADSP record at all. The organization does not make any guarantees about how consistently they use DKIM to sign their e-mails. All states that all e-mail from an organization will be DKIM signed. Discardable states that in addition to All, the organization wants any non-signed e-mail to be silently discarded by the receiving party.

Away messages – If these sick/vacation messages are sent as replies to Junk Mail, you are simply going to respond to spammers. Again, because of forgeries, such messages can be sent as spam to innocent addresses, or sent to non-existent addresses and bounced back yet again as a DSN. Never reply to spam!

Backscatter – While some administrators might think they are being neighborly and helping out a fellow netizen, most Spam and Viri is delivered using forged from addresses. These forged addresses sometimes receive a lot of Delivery Status Notifications or DSNs. This is called backscatter.

So, please, don’t bounce spam, as this causes backscatter! This can also get you blacklisted.

Bayesian Classifier – The Bayesian Classifier in SpamAssassin learns tokens – words or short sequences – that are commonly found in spam or ham. It makes use of Bayes’ Theorem, with strong assumptions about the statistically independent nature of e-mail. Bayesian classifiers make an effective means of adapting to new spam techniques, by adding uncaught spam to the spam/ham datasets to improve the classifier’s accuracy.

Blacklist / Whitelist – These are lists of domains, IP addresses, or other means of identifying the sender of a message. A blacklist contains entries intended to identify spammers, while a whitelist identifies known-good senders. Some common blacklists are below. You should research the rules and limits of each list before using them.

Other blacklist checkers:

Challenge and Response – Another similar technique that causes DSNs is called Challenge and Response. This is a system where a new sender is sent an e-mail by an automated system asking them to verify that they sent the original e-mail. Unfortunately, because of forgeries, C+R systems are often considered spam. Use it at your own risk!

Checksum blacklist – A particular type of blacklist containing hashes or checksums of known spam messages. This can be a quick way of detecting some of the most common spam messages. For information on using a checksum blacklist with SpamAssassin, see perldoc Mail::SpamAssassin::Plugin::DCCperldoc Mail::SpamAssassin::Plugin::Pyzor, and perldoc Mail::SpamAssassin::Plugin::Razor2. Cloudmark is a commercial derivative of the Razor checksum filter.

DMARC – “Domain-based Message Authentication, Reporting & Conformance” is a standardized way for an e-mail sender to inform the recipient that the e-mails are protected by SPF and/or DKIM, and what to do in the event that these procedures fail. DMARC removes any guesswork about what to do with an e-mail if it fails, limiting or eliminating the user’s exposure to potentially fraudulent and harmful messages. DMARC doesn’t directly address whether or not an e-mail is spam or otherwise fraudulent. DMARC also provides a way for the e-mail receiver to report back to the sender about messages that pass and/or fail DMARC evaluation.

Information/Websites used in creation of this text –
http://dmarc.org/
http://en.wikipedia.org/wiki/DMARC

False positives and negatives – Much like testing for an illness, e-mail tests positive for being spam and test negative for being legitimate. A false positive is when a legitimate e-mail is mistakenly marked as spam. A false negative is when a spam e-mail is mistakenly accepted as legitimate.

One of the core principles of anti-spam is Do No Harm. It is better to let a thousand spam e-mails through than to drop even a single legitimate one. This can sometimes be very difficult. A common scam e-mail tactic is to forge an e-mail from a friend, saying they are on vacation and need money for a taxi, if you could just send it to their account. Obviously, an accounting firm would be very unhappy if their spam filter reacted to such tactics with a uniform block on any banking-related keywords.

The vast majority of Spam uses forged sender addresses as we talked about with the Reduction of DSNs. If you whitelist your own domain, you are just going to whitelist a whole bunch of Spam! Deploying SPF (as well as DKIM & ADSP) will help combat these forgeries and there are rules for these technologies that can decrease AND increase the overall score for an e-mail.

Greylist – A greylist contains senders about which you are undecided. Your server will return a temporary error to every greylisted sender, requiring them to connect twice to send an e-mail. This technique can block most spam sent by poorly-written software that cannot handle temporary 4XX errors correctly. Greylisting is not recommended though, because it also blocks e-mail from poorly-written software that sends legitimate e-mails. It purposefully introduces a delay in the sending of legitimate e-mail, and reports spurious errors that can make it difficult to determine when your server is having a real problem.

rPTR, Smart Hosts, and SPF – On the internet, computers speak in numbers called in IP addresses. Humans use names via DNS to translate into the numbers. However, you can also translate a number into a name. This is called a reverse lookup.

Having a valid answer for a reverse lookup, called a reverse PTR or rPTR makes your mail server more legitimate. Some ISPs, like AOL, will not even accept e-mail from a server that doesn’t have one. A reverse lookup should match exactly. For example, mail.macsysadmin.se instead of static-71-163-15-129.washdc.fios.verizon.net.

If you don’t have a static IP, you really MUST be using a Smart Host. This is the feature in the mail preferences to Relay E-mail through your ISP. Mark Martinec, another member of the SA Project Management Committee, also points out that you should really, really use the Smart Host or MSA of a domain used in your From address. Submitting mail through anything but the MSA for the From address will likely contribute points towards the threshold to tag an e-mail as Spam.

So, via your user’s Mail User Agent, they should be submitting the e-mail to your domain’s Mail Submission Agent, preferably on a standard submission port 587 and authenticated through AUTH or POP-Before-SMTP or similar. In the same vein, when using @gmail.com in the From address, the e-mail should be submitted through that domains MSA, smtp.gmail.com:587. The Gmail web interface, technically just another MUA, would automatically be setup to use a proper submission method.

The reason away from using an ISP’s Smart Host to an MSA for the domain is due to the widespread e-mail address forgery in Junk Mail. This fraud has necessitated increasingly stricter methods to distinguish the valid addresses from the forged address. One of these stricter methods is SPF.

Using these methods, like SPF or Sender Policy Framework by adding an SPF Record for your domain will help control forged e-mail. SPF allows other servers that receive your e-mails to check your domain’s DNS. There you can set policies that tell the MTA on the receiving end what MTAs are allowed to transmit e-mail for your domain. The website www.openspf.org can assist you in configuring this record.

Dictionary

AMaViS- A Mail Virus Scanner – A Mail Virus Scanner scans e-mail attachments for viruses using third-party applications available for UNIX operating systems. It is written in Perl, and is the application which calls SpamAssassin in OS X.

https://gitlab.com/amavis/amavis
https://www.amavis.org/

Backscatter (outscatter and misdirected bounces, blowback, or collateral spam, et al.) – A side effect of e-mail spam, viruses, and worms where e-mail servers receiving spam and other mail send bounce messages to innocent users. These usually come in the form of “Your mail could not be delivered..” or “Your mail contained a virus..” messages. These messages are classified as spam because they aren’t solicited by the recipient and are delivered in bulk quantity. The vast majority of SPAM comes from forged e-mail addresses.

Information/Websites used in creation of this text –
http://www.spamresource.com/2007/02/backscatter-what-is-it-how-do-i-stop-it.html
http://en.wikipedia.org/wiki/Outscatter

Blacklist (See DNSBLs) – a basic access control mechanism that allows every access, except for the members of the black list (i.e. list of denied accesses). The opposite is a whitelist, which means allow nobody, except members of the white list. As a sort of middle ground, a greylist, contains accesses that are temporarily blocked.

Information/Websites used in creation of this text –
http://en.wikipedia.org/wiki/Blacklist_%28computing%29

Deep Header Parsing aka Deep Header Inspection – Some anti-spam tools will actually look at the reputation of IP addresses in each of the received headers of an e-mail. Reputation mechanisms usually involve multiple sources, e.g., DNSBLs and Honeypot-driven reputation services.

Here’s a sample header:

Delivered-To: address@gmail.com Received: by [[1.1.1.1]] with SMTP id e5cs33412ibd; Fri, 16 Apr 2010 08:38:08 -0700 (PDT) Received: by [[1.2.2.2]] with SMTP id e9mr1978437rvi.51.1271432287560; Fri, 16 Apr 2010 08:38:07 -0700 (PDT) Return-Path: me@mydomain.com Received: from SERVER.somedomain.com (mail.somedomain.com [[3.3.3.3]]) by mx.google.com with ESMTP id 11si4715430qyk.0.2010.04.16.08.38.06; Fri, 16 Apr 2010 08:38:07 -0700 (PDT) Received: from myserver.mydomain.com (unverified [[4.4.4.4]]) by SERVER.somedomain.com (XYZ MTA) with ESMTP id <B0001262286@SERVER.somedomain.com> for <address@gmail.com>; Fri, 16 Apr 2010 11:38:08 -0400 [BRACKETED]: IP addresses that will be verified.

http://www.emailsecuritymatters.com/site/blog/best-practices/deep-header-inspection-use-with-caution/
http://www.spamhaus.org/pbl/

DomainKeys Identified Mail (DKIM) – an e-mail authentication system which verifies the domain of a sender. It resulted from the combination of DomainKeys and Identified Internet Mail. A server can therefore identify e-mails from forged e-mail addresses and identify it as spam.

A domain owner generates private/public key-pairs that will be used to sign messages originating from that domain. The public-key is placed in DNS as a text file. The private-key is kept on the mail server which sends e-mail for the domain. When a user sends an e-mail, the e-mail is embedded with a digital signature based on the private key and sent. The receiving server uses the domain name and elements in the key to perform a DNS lookup for a specified text file in the digital signature to find the public key. If the e-mail passes this lookup, it is legitimate.

ADSP is an optional extension to DKIM.

http://en.wikipedia.org/wiki/DomainKeys_Identified_Mail
http://www.elandsys.com/resources/sendmail/domainkeys.html
http://www.dkim.org/

DNFTEC – This acronym goes all the way back to 1996. Its the original “don’t feed the trolls.” DNFTEC stands for ‘don’t feed the energy creatures’ and a great description of what/who these are can be found here:

http://www.cryonet.org/cgi-bin/dsp.cgi?msg=6284

“There is a certain type of being that’s all too common in the online world. I call them “Energy Creatures,” a term I first heard on one of the commercial services. Energy Creatures are a bizarre lifeform which grow and feed off of the negative energy generated by others.

Energy Creatures’ favorite feeding tactic is to try to hurt people’s feelings or get them angry. Then they can feed off the pain and anger they’ve generated. Their second favorite tactic is to hurt one person or group’s feelings while gathering the sympathy of others. That way, when the injured party lashes back, others will jump to the Energy Creature’s defense. Then the Energy Creature need do nothing except feed off the attention and the negative energy generated by the people fighting.”

While energy creatures are normally thought to frequent the various forums around the internet, the same term can be applied to spam mailers. Its more common today to find that spammers are actually members of organized crime around the world or are hackers with large robotic networks of hijacked computers called botnets. These fall under the DNFTEC acronym because they are trying to steal your money, personal information, contact information, of all of the above. PCCC highly recommends that users just mark the spam mail as such and move on. Do not hit the ‘click here to be removed from our list’ link since most of the time those just confirm to the spammers which e-mails addresses are actually live.

DNS – The Domain Name System (DNS) is an internet directory service. DNS’s most basic service is to translate hostnames into IP addresses, and DNS also controls e-mail delivery. If your computer cannot access DNS, your web browser will not be able to find web sites, and you will not be able to receive or send e-mail. The DNS system consists of three components: DNS data (called resource records), servers (called name servers), and Internet protocols for fetching data from the servers. The billions of resource records in the DNS are split into millions of files called zones. Zones are kept on authoritative servers distributed all over the Internet, which answer queries based on the resource records stored in the zones they have copies of. Caching servers ask other servers for information and cache any replies. Most name servers are authoritative for some zones and perform a caching function for all other DNS information. Large name servers are often authoritative for tens of thousands of zones, but most name servers are authoritative for just a few zones.

Information/Websites used in creation of this text –
http://www.dns.net/dnsrd/docs/whatis.html
http://en.wikipedia.org/wiki/Domain_Name_System

DNS Blacklist (DNSBL) – A published list of IP addresses that can be queried through the Internet. DNSBLs are used to publish IP addresses associated with e-mail spam and spamming. Most mail servers can be configured to reject messages from addresses on a DNSBL. An address found in a DNSBL may be directly associated with spam, or may have made the list due to Web server vulnerabilities that can be used by spammers. There are many DNSBLs available, each published and maintained by different individuals and organizations.

Information/Websites used in creation of this text –
http://www.webopedia.com/TERM/D/DNSBL.html
http://en.wikipedia.org/wiki/DNSBL

DSNs – Delivery Status Notification – DSNs are automated e-mail messages from a mail system informing the sender of the status of his/her e-mail.

DSNS are classified in these categories

  • 2xx/3xx – successful
  • 4xx – failure, asking sender to try later
  • 5xx – permanent failure

2xx/3xx class – Success Messages

  • 200 Non standard success response
  • 211 System status, or system help reply
  • 214 Help message
  • 220 Service ready
  • 221 Service closing transmission channel
  • 250 Requested mail action taken and completed – Your ISP mail server has successfully executed a command and the DNS is reporting a positive delivery.
  • 251 User not local: will forward to: – Your message to a specified e-mail address is not local to the mail server, but it will accept and forward the message to a different recipient e-mail address.
  • 252 Recipient cannot be verified – Recipient cannot be verified but mail server accepts the message and attempts delivery
  • 354 Start mail input and end with . – Indicates mail server is ready to accept the message or instruct your mail client to send the message body after the mail server has received the message headers.

4xx class – Temporary Errors – Those codes are temporary error messages. They are used to tell the sender that an error occured and to try later.

  • 421 Service not available, closing transmission channel – This may be a reply to any command if the service knows it must shut down.
  • 450 Requested mail action not taken: mailbox busy or access denied – Your ISP mail server indicates that an e-mail address does not exist or the mailbox is busy. It could be the network connection went down while sending, or it could also happen if the remote mail server does not want to accept mail from you for some reason i.e. (IP address, From address, Recipient, etc.)
  • 451 Requested mail action aborted: error in processing – Your ISP mail server indicates that the mailing has been interrupted, usually due to overloading from too many messages or transient failure is one in which the message sent is valid, but some temporary event prevents the successful sending of the message. Sending in the future may be successful.
  • 452 Requested mail action not taken: insufficient system storage – Your ISP mail server indicates, probable overloading from too many messages and sending in the future may be successful.
  • 453 Too many messages – Some mail servers have the option to reduce the number of concurrent connection and also the number of messages sent per connection. If you have a lot of messages queued up it could go over the max number of messages per connection. To see if this is the case you can try submitting only a few messages to that domain at a time and then keep increasing the number until you find the maximum number accepted by the server.

5xx class – Permanent Errors – These are permanent error codes. Mail transfer is definitly a failure. No other try will be done.

  • 500 Syntax error, command unrecognized or command line too long
  • 501 Syntax error in parameters or arguments
  • 502 Command not implemented
  • 503 Server encountered bad sequence of commands
  • 504 Command parameter not implemented
  • 521 does not accept mail or closing transmission channel – You must be pop-authenticated before you can use this SMTP server and you must use your mail address for the Sender/From field.
  • 530 Access denied – A sendmailism ?
  • 550 Requested mail action not taken (Relaying not allowed, Unknown recipient user, …) – Sending an e-mail to recipients outside of your domain are not allowed or your mail server does not know that you have access to use it for relaying messages and authentication is required. Or to prevent the sending of SPAM some mail servers will not allow (relay) send mail to any e-mail using another company’s network and computer resources.
  • 551 User not local: please try or Invalid Address: Relay request denied
  • 552 Requested mail action aborted: exceeded storage allocation – ISP mail server indicates, probable overloading from too many messages.
  • 553 Requested mail action not taken: mailbox name not allowed – Some mail servers have the option to reduce the number of concurrent connection and also the number of messages sent per connection. If you have a lot of messages queued up (being sent) for a domain, it could go over the maximum number of messages per connection and/or some change to the message and/or destination must be made for successful delivery.
  • 554 Requested mail action rejected: access denied
  • 557 Too many duplicate messages – Resource temporarily unavailable Indicates (probable) that there is some kind of anti-spam system on the mail server.

http://en.wikipedia.org/wiki/Non_delivery_report
http://tools.ietf.org/html/rfc3461

Internet Message Access Protocol (IMAP) – a method of accessing electronic mail or bulletin board messages that are kept on a (possibly shared) mail server. In other words, it permits a “client” e-mail program to access remote message stores as if they were local. For example, e-mail stored on an IMAP server can be manipulated from a desktop computer at home, a workstation at the office, and a notebook computer while traveling, without the need to transfer messages or files back and forth between these computers. IMAP’s ability to access messages (both new and saved) from more than one computer has become important as reliance on electronic messaging and use of multiple computers increase, but this functionality cannot be taken for granted: the widely used Post Office Protocol (POP) works best when one has only a single computer, since it was designed to support “offline” message access, wherein messages are downloaded and then deleted from the mail server.

Information/Websites used in creation of this text –
http://en.wikipedia.org/wiki/IMAP
http://www.imap.org/about/whatisIMAP.html

IMAP4 Testing – IMAP can be tested using the following list of commands:

telnet 143 - THIS ESTABLISHES A CONNECTION TO THE DOVECOT IMAP SERVER AT
abc1 login - THIS LOGS IN THE USER USING THEIR PASSWORD
abc1 select inbox - THIS CHECKS THAT THE INBOX CAN BE FOUND
#IF THERE IS A MESSAGE IN THE INBOX YOU COULD REVIEW IT
abc1 fetch 1 body[text] - THIS SHOWS A TEST MESSAGE IN "INBOX" FOR THE USER
abc1 logout - closes the connection to dovecotIMAP on :143

Glue – The method in which one program is interfaced with another. There are many ways of doing this including using a program.s API, calling the other program directly, etc. SpamAssassin can be called in multiple ways and ‘glued’ into various filtering methods.

http://en.wikipedia.org/wiki/Glue_code

GNU-Unix-like Operating System – A Unix-like operating system that aims to be a complete Unix-compatible operating system consisting of completely free software.

http://en.wikipedia.org/wiki/GNU

GPG – GNU Privacy Guard – A protection system that encrypts data to be sent to another computer. It was created in the GNU Project, but now is compatible most operating systems. You can install a GPG plugin on OS X Mail called GPGMail.

http://en.wikipedia.org/wiki/GNU_Privacy_Guard

HELO greeting (pertaining to AntiSpam) – Spam can be greatly reduced by a number of checks confirming compliance with standard addressing and MTA operation. In many situations, simply requiring a valid FQDN (Fully Qualified Domain Name) in the SMTP HELO statement is enough to block 25% of incoming spam.

  • Refusing connections from hosts that begin transmission prior to presentation of the receiving host’s HELO banner.
  • Refusing connections from hosts that give an invalid HELO – for example, a HELO that is not an FQDN or is an IP address not surrounded by square brackets
    Example:

    Invalid: HELO localhost
    Invalid: HELO 127.0.0.1
    Valid: HELO domain.tld
    Valid: HELO [127.0.0.1]

  • Refusing connections from hosts that give an obviously fraudulent HELO – for example, issuing a HELO using the FQDN or an IP address that doesn’t match the IP address of the connecting host

    Fraudulent: HELO friend
    Fraudulent: HELO -232975332

  • Refusing to accept e-mail claiming to be from a hosted domain when the sending host has not authenticated
  • Refusing to accept e-mail whose HELO/EHLO argument does not resolve in DNS. Unfortunately, some e-mail system administrators ignore section 3.6 of RFC2821 and administer the MTA to use a nonresolvable argument to the HELO/EHLO command. All of the examples above are fairly simple checks, all conform to existing standards and RFCs, and all are missing from most commercial MTA implementations available today.

Information/Websites used in creation of this text –
http://en.wikipedia.org/wiki/Anti-spam_techniques_%28email%29#HELO.2FEHLO_checking

Lightweight Directory Access Protocol (LDAP) – LDAP is an Internet protocol that e-mail and other programs use to look up information from a server. LDAP is used to look up encryption certificates, pointers to printers and other services on a network, and provide “single sign-on” where one password for a user is shared between many services. LDAP is appropriate for any kind of directory-like information, where fast lookups and less-frequent updates are the norm. As a protocol, LDAP does not define how programs work on either the client or server side. It defines the “language” used for client programs to talk to servers (and servers to servers, too). On the client side, a client may be an e-mail program, a printer browser, or an address book. The server may speak only LDAP, or have other methods of sending and receiving data—LDAP may just be an add-on method.

LDAP also defines:
Permissions: set by the administrator to allow only certain people to access the LDAP
database, and optionally keep certain data private.
Schema: a way to describe the format and attributes of data in the server.

Information/Websites used in creation of this text –
http://www.gracion.com/server/whatldap.html
http://en.wikipedia.org/wiki/LDAP

Milters – Midstream Filters – A milter enables third-party programs to access mail messages as they are being processed by the MTA. A milter allows them to examine and modify content and the meta-information.

Previously, the MTA would pass the e-mail to an e-mail filter for filtering after the e-mail was completely downloaded. With a milter-capable MTA, it instead does all this work while the e-mail is being downloaded. This allows rejection of massive files very early on to prevent wasted downloading.

At each phase of the SMTP session, the filter is given data about the arriving message and then has an opportunity to make decisions concerning the message. For very large messages, this can have an enormous impact such as when a decision to reject can be made as early as possible. Moreover, unlike the former model, a milter-capable MTA can connect to multiple filters in parallel that serve specific purposes such as anti-virus, anti-spam, message authentication, flow regulation, etc. Finally, such filters can take special action on the message: add or remove recipients in the envelope; alter the body prior to delivery; add, change or remove header fields in the message, etc.

For example, a very cursory look at our Raptor system shows that:

  1. During the SMTP conversation, the mail is filtered by MIMEDefang. If the mail is being forwarded, MD calls SpamAssassin and the mail is scanned for Spam.
  2. AFTER the SMTP Conversation concludes (by replying to the final “.” with a 2xx SMTP reply code), the Milter has one more pass at the e-mail and if the mail is delivered locally, the mail gets handed over to the delivery agent. In our case, that’s procmail.
  3. For local users, spamassassin is called by the global /etc/procmailrc script as part of the MDAs work. When the spamc command returns (possibly having altered the mail), procmail drops it into your INBOX.
  4. For non-local users, MD can be configured to spam test the e-mail prior to delivery

See also MIMEDefang for an example of “a milter”.

http://en.wikipedia.org/wiki/Milter
https://www.milter.org/

Phishing – A social engineering technique used by bodies posing as a trustworthy source to steal information (i.e. – usernames/passwords, bank/PayPal account information, any information that can be used to assist in data and/or identity theft.). These attacks are typically carried out via e-mail or instant messaging and in some cases through bogus accounts on social networking services such as MySpace, Facebook, etc.

E-mail deception usually takes the form of a link in a bogus e-mail or IM (though the e-mail can be VERY convincing down to being an almost Exact copy of a legitimate e-mail from the company being “spoofed” using company logos and appearing very ‘official looking’.) which leads to a website where the user being scammed will input sensitive information thus completing the theft. Requests to “verify your account” are often used in these fraudulent messages with links that appear to lead to the legitimate website to ‘verify your account’ but actually lead to the websites mentioned previously.

Phishers employ various other tactics in attempts to trick you into following their links and submitting confidential information. These techniques include Link Manipulation such as, Misspelled URLs(www.paypa1.com rather than www.paypal.com),and Masked URL, making the anchor text of a link appear valid but on mouseover in the tooltip that appears you will see where the link is Actually pointing to the scam site. Also, Filter Evasion is a common technique, using images with text on them instead of actual text in an e-mail to avoid anti-phishing filters searching for text commonly used in phishing e-mails.

Not all phishing attacks require a fake website. Scammers can employ VOIP numbers to call users claiming to need Account and PIN numbers for different services. The caller ID can be spoofed to show a legitimate company or organization name. This technique of Voice Phishing is called “Vishing”.

Damage caused by phishing ranges from denial of access to e-mail to substantial financial loss.

Information/Websites used in creation of this text –
http://www.microsoft.com/protect/yourself/phishing/identify.mspx
http://en.wikipedia.org/wiki/Phishing

Protocol (i.e. – POP,IMAP,etc.) before SMTP – Protocol (POP will be used in this text) before SMTP is a method of authorization used by mail server software which helps allow users the option to send e-mail from any location, as long as they can demonstrably also fetch their mail from the same place. Users are allowed to use SMTP from an IP address as long as they have previously made a successful login into the POP service at the same mail hosting provider, from the same IP address, within a predefined timeout period. The main advantage of this process is that it’s generally transparent to the average user who will be connecting with an e-mail client, which will almost always make a connection to fetch new mail before sending new mail. The disadvantages include a potentially complex setup for the mail hosting provider (requiring some sort of communication channel between the POP service and the SMTP service) and uncertainty as to how much time users will take to connect via SMTP (to send mail) after connecting to POP. Those users not handled by this method need to resort to other authorization methods. Also, in cases where users come from externally controlled dial-up addresses (more specifically, all dynamically assigned IP addresses), the SMTP server must be careful about not giving too much leeway when allowing unauthorized connections, because of a possibility of race conditions leaving an open mail relay unintentionally exposed.

Information/Websites used in creation of this text –
http://en.wikipedia.org/wiki/POP_before_SMTP
http://popbsmtp.sourceforge.net/

Post Office Protocol (POP3) – an application-layer Internet standard protocol, to retrieve e-mail from a remote server over a TCP/IP connection. The design of POP3 and its procedures supports end-users with intermittent connections (such as dial-up connections), allowing these users to retrieve e-mail when connected and then to view and manipulate the retrieved messages without needing to stay connected. Although most clients have an option to leave mail on server, e-mail clients using POP3 generally connect, retrieve all messages, store them on the user’s PC as new messages, delete them from the server, and then disconnect. This standard protocol is built into most popular e-mail products, such as Eudora and Outlook Express. It’s also built into the Netscape and Microsoft Internet Explorer browsers. POP3 is designed to delete mail on the server as soon as the user has downloaded it. However, some implementations allow users or an administrator to specify that mail be saved for some period of time. POP can be thought of as a “store-and-forward” service. An alternative protocol is Internet Message Access Protocol (IMAP). IMAP provides the user more capabilities for retaining e-mail on the server and for organizing it in folders on the server. IMAP can be thought of as a remote file server.

Information/Websites used in creation of this text –
http://searchexchange.techtarget.com/sDefinition/0,,sid43_gci212805,00.html
http://en.wikipedia.org/wiki/POP3

POP3 Testing – Test POP3 by running the following commands:

telnet 110 - THIS ESTABLISHES A CONNECTION TO 2004.89 POP3 SERVER
user - THIS LOGS IN
pass - THIS AUTHENTICATES WITH THE MAIL SERVER
YOU WILL RECIEVE NOTIFICATION THAT "+OK mailbox open, Messages (where XXX is the number of messages in your inbox)
retr (WHERE XXX IS THE NUMBER OF THE MESSAGE YOU WOULD LIKE TO RETRIEVE, 1 BEING THE FIRST MESSAGE IN THE BOX) - THIS RETRIEVES AND DISPLAYS ON-SCREE IN PLAIN TEXT 'AND' HTML THE SPECIFIED MAIL MESSAGE
quit - SIGNS OUT OF THE CURRENT TELNET SESSION WITH THE POP3 SERVER

POP vs. IMAP – POP and IMAP both have various Pros and Cons associated with each protocol.

Advantages of POP3 include:

Message storage is limited only by the capacity of your computer.
Minimum use of connect time.
Minimum use of server resources.
It is less likely to exhaust disk space on the server.

Disadvantages to POP3 include:

Reading your e-mail from multiple computers or e-mail programs results in messages scattered about.
Messages are stored on your computer. If your computer fails you may lose all your e-mail.
You are not able to preview new messages before downloading, nor do you have control over which messages can be downloaded.
Once delivered, e-mail messages are stored on your local computer and deleted from the mail server.

Advantages of IMAP include:

Messages are stored on the server and are not affected if your computer fails.
Easily use multiple computers or e-mail programs to read mail.
Faster start-up time, as only message headings are transferred initially
Optimization for low-speed connections.

Disadvantages to IMAP include:

Mail is not usually available if you are offline.
Sensitive to size and requires periodic archival of e-mail messages
Subject to storage quotas
Very few ISPs and e-mail providers offer IMAP as it is considered a high end option and it’s complex for them to support
Not all e-mail programs support it properly

Information/Websites used in creation of this text –
http://saturn.med.nyu.edu/it/help/email/imap/index.html
http://www.washington.edu/computing/windows/issue13/imap_pop.html
http://www.uoregon.edu/~mcshtml/email/popvsimap.html
http://www.it.northwestern.edu/accounts/email/imap/pop-imap-comparison.html

Why Port 25 is Blocked and Alternate Ports that Are available

Port 25 is often blocked by ISPs to help inhibit the distribution of spam. “But I’m not a spammer!” Many people say that and many people aren’t spammers, but times are changing. As noted above in the DNFTEC section, more and more spammers are actually members of organized crime or just hackers in general. Many pieces of malware that are out in the wild don’t do anything except make your computer a member of a larger network of hijacked computers called a botnet. Botnets can be very useful to people with bad intentions. Spammers use botnets to send out their millions of spam messages to the internet and as a result, eat bandwidth. The reason ISPs block port 25 is just in case your computer gets hijacked and becomes part of a botnet, it can’t automatically send out e-mail.

http://www.pccc.com/base.cgim?template=port_25_blocked

Ports like 2025, 2525 are non-standard ports that some ISPs provide. There is no standard to these port #’s.

587 is a standard submission port. It requires authentication and more ISPs are supporting (or even requiring) you to use this port.

465 is a standard SMTPS or SMTP over SSL port.

postmaster.aol.com – presents a set of standards, guidelines, and best practices regarding e-mail policy.

Information/Websites used in creation of this text –
http://postmaster.aol.com/guidelines/

Real-time Blacklist (RBL) – The first DNSBL (DNS Blacklist) was the Real-time Blackhole List (RBL). Initially, the RBL was not a DNSBL, but rather a list of commands that could be used to program routers so that network operators could blackhole, a routing term to send all the packets into nothingness, all TCP/IP traffic for machines used to send spam or host spam supporting services, such as a website. The purpose of the RBL was not simply to block spam—it was to educate Internet service providers and other Internet sites about spam and related problems, such as open SMTP relays, spamvertising, etc. The RBL was also released in a DNSBL form and authors of Sendmail and other mail software were urged to implement RBL clients. This allowed the mail software to query the RBL and reject mail from listed sites on a per mail server basis instead of “blackholing” all traffic.

Information/Websites used in creation of this text –
http://en.wikipedia.org/wiki/Real-time_Blackhole_List#Terminology

Reverse DNS (rDNS) – rDNS is a process to determine the hostname or host associated with a given IP address or host address. Reverse DNS is setup by configuring PTR records (Pointer Records) in your DNS server. The Domain Name System is used to determine what IP address is associated with a given domain name. So, to reverse DNS lookup an IP address is to look up what host and domain name belongs to that IP address. There are many reverse DNS lookup tools available for free on the internet at various sites.

Information/Websites used in creation of this text –
http://www.tech-faq.com/reverse-dns.shtml
http://en.wikipedia.org/wiki/Reverse_DNS

Request for Comments (RFC) – Documents published as a series of memos encompassing new research, innovations, and methodologies applicable to internet technologies for review by peers or to convey new technologies/protocols. The Internet Engineering Task Force (IETF) adopts RFCs as Internet Standards.

Information/Websites used in creation of this text –
http://en.wikipedia.org/wiki/Request_for_Comments

RFC-Ese (RFC 2119) – It’s important to understand this RFC to understand RFCs in general as it works to remove some of the vagueness of the English language that might otherwise creep up when interpreting RFCs and similar technical documentation.

Taken from http://www.ietf.org/rfc/rfc2119.txt

  1. MUST – This word, or the terms “REQUIRED” or “SHALL”, mean that the definition is an absolute requirement of the specification.
  2. MUST NOT – This phrase, or the phrase “SHALL NOT”, mean that the definition is an absolute prohibition of the specification.
  3. SHOULD – This word, or the adjective “RECOMMENDED”, mean that there may exist valid reasons in particular circumstances to ignore a particular item, but the full implications must be understood and carefully weighed before choosing a different course.
  4. SHOULD NOT – This phrase, or the phrase “NOT RECOMMENDED” mean that there may exist valid reasons in particular circumstances when the particular behavior is acceptable or even useful, but the full implications should be understood and the case carefully weighed before implementing any behavior described with this label.
  5. MAY – This word, or the adjective “OPTIONAL”, mean that an item is truly optional. One vendor may choose to include the item because a particular marketplace requires it or because the vendor feels that it enhances the product while another vendor may omit the same item. An implementation which does not include a particular option MUST be prepared to interoperate with another implementation which does include the option, though perhaps with reduced functionality. In the same vein an implementation which does include a particular option MUST be prepared to interoperate with another implementation which does not include the option (except, of course, for the feature the option provides.)
  6. Guidance in the use of these Imperatives
    Imperatives of the type defined in this memo must be used with care and sparingly. In particular, they MUST only be used where it is actually required for interoperation or to limit behavior which has potential for causing harm (e.g., limiting retransmisssions) For example, they must not be used to try to impose a particular method on implementors where the method is not required for interoperability.
  7. Security Considerations
    These terms are frequently used to specify behavior with security implications. The effects on security of not implementing a MUST or SHOULD, or doing something the specification says MUST NOT or SHOULD NOT be done may be very subtle. Document authors should take the time to elaborate the security implications of not following recommendations or requirements as most implementors will not have had the benefit of the experience and discussion that produced the specification.

http://tools.ietf.org/html/rfc2119
http://www.ietf.org/rfc/rfc2119.txt

rPTR (see rDNS) – Reverse DNS is a way of associating an IP address with its domain name. The reverse DNS identifier is contained in the PTR portion of the IP Zone File. The IP Zone File contains all the different ways that your IP and domain name can be associated; each association serves a different need.

Information/Websites used in creation of this text –
http://postmaster.aol.com/info/rdns.html

SMTP – Simple Mail Transfer Protocol (SMTP) is the standard for e-mail transmission across the internet. A relatively simple text-based protocol, SMTP is limited in its ability to queue messages at the receiving end, it is usually used with one of two other protocols, POP3 or IMAP, that let the user save messages in a server mailbox and download them periodically from the server. Extended SMTP(ESMTP) is the protocol used today and allows for multimedia files to be delivered as e-mail.

Information/Websites used in creation of this text –
http://en.wikipedia.org/wiki/SMTP
http://searchexchange.techtarget.com/sDefinition/0,,sid43_gci214219,00.html

SMTP Testing – SMTP can be tested using the following list of commands:

telnet 25 - THIS ESTABLISHES A CONNECTION TO THE SMTP SENDMAIL SERVER
helo - THIS IS THE "HELO"(aka "Hello") GREETING, INITIATING DIALOG WITH THE MAIL SERVER BY IDENTIFYING THE MACHINE YOU'RE USING.
mail from:
rcpt to:

data subject:

<– THIS MUST END IN A <.>
. <– INPUT A PERIOD, THIS “SENDS” THE MESSAGE AT WHICH POINT THE SERVER WILL PROVIDE A DSN REGARDING YOUR SENT MESSAGE
quit – THIS ENDS THE SESSION WITH THE SMTP SERVER

SMTP AUTH – SMTP-AUTH is an extension of the Simple Mail Transfer Protocol (SMTP) to include an authentication step through which the client effectively logs in to the mail server during the process of sending mail. Servers which support SMTP-AUTH can usually be configured to require clients to use this extension, ensuring the true identity of the sender is known. SMTP-AUTH is defined in RFC 4954.

Information/Websites used in creation of this text –
http://en.wikipedia.org/wiki/SMTP_AUTH

Sender Policy Framework (SPF) – SPF is an anti-forgery system in which the Internet domain of an e-mail sender can be authenticated for that sender, thereby discouraging spam mailers, who routinely disguise the origin of their e-mail, a practice known as e-mail spoofing. SPF allows the owner of an Internet domain to use a special format of DNS TXT records to specify which machines are authorized to transmit e-mail for that domain. For example, the owner of the example.org domain can designate which machines are authorized to send e-mail whose sender e-mail address ends with “@example.org”. Receivers checking SPF can reject messages from unauthorized machines before receiving the body of the message. Principles of operations are quite similar to those of DNSBL, except that SPF exploits the authority delegation scheme of the real Domain Name System. SPF and other authentication-based measures are designed to redress a vulnerability in Simple Mail Transfer Protocol (SMTP), the main protocol used in sending e-mail, which does not include an authentication mechanism.

Information/Websites used in creation of this text –
http://searchsecurity.techtarget.com/sDefinition/0,,sid14_gci953520,00.html
http://en.wikipedia.org/wiki/Sender_Policy_Framework

TTL – (Time to Live) – Occur in the Domain Name System (DNS), where they are set by an authoritative nameserver for a particular resource record. When a caching nameserver queries the authoritative nameserver for a resource record, it will cache that record for the time (in seconds) specified by the TTL. Shorter TTLs can cause heavier loads on an authoritative nameserver, but can be useful when changing the address of critical services like web servers or MX records, and therefore are often lowered by the DNS administrator prior to a service being moved, in order to minimize disruptions.

Information/Websites used in creation of this text –
http://en.wikipedia.org/wiki/Time_to_live#Time_to_live_of_DNS_records

How to send email that will be stopped as spam

By Dianne F. Skoll

How to send e-mail that will be stopped as SPAM

Why?

How many times have you been required to send an e-mail to someone, but really didn’t want to? You know, those pesky class assignments that you have not bothered to work on, your sample resume for your dad to check out. Well now I’ll let you know how you can send those e-mails and have them not get to the destination so that you can tell your dad/professor: “I did send it, but the stupid SPAM scanners rejected it as SPAM.”

The Methods

  1. Send e-mail that has an attachment but no message in the body
    Just attach whatever spreadsheet/document to your e-mail and put no text in the body. SPAM scanners score this very high. Many times this is enough in itself to get your e-mail rejected.
  2. Send e-mail with profanity in the Subject
    Though this does not score as high as the first method it does score quite high. This works because most SPAM scanners really want to stop that porn SPAM. This works even better if you try to obfuscate the profanity with something like spaces, periods, asterisks between the letters.
  3. Send e-mail with profanity in the body of the mail
    Sort of like number 2 but does not score quite as high. Trying to obfuscate the profanity will raise the score more though. Don’t zip up the body and send it as an attachment (unless you do it with no text in the body (#1)) because the SPAM scanners don’t check for profanity in a zip file.
  4. Send e-mail with a Word document as an attachment
    Word documents as attachments really raise the score nicely.
    Remember though, don’t zip them up or they won’t raise the score. Besides, zipping them would make your e-mail smaller and easier to deliver.
  5. Send e-mail with no Subject
    Not putting a subject on your e-mail scores fairly high as well.
  6. Send e-mail with a Subject that is all CAPS
    This is a surprisingly simple method that will raise the SPAM score
  7. Send e-mail with the body in all CAPS
    Combined with #6 this can be fairly effective in upping your SPAM score

Summary
If you combine methods, you greatly improve chances of getting your mail stopped as SPAM. For instance, if you attach a word document #4, with no text in the body #1, and either no subject #5, or a subject that is all caps #6 you can pretty much guarantee that your e-mail will be rejected as SPAM. Hey, check back once in a while, I’ll probably be adding new methods for you to employ.

Source PDF

Acknowledgements

This compendium was compiled and edited by Kevin A. McGrail

This page consists of information assembled from various sources with contributions from:

  • Dorian Chan for his work as part of the Google Code-In
  • Dianne F. Skoll and MIMEDefang
  • Robert Schetterer
  • The Perl foundation, Google Code-In
  • PCCC
  • The Apache Software Foundation SpamAssassin Project Management Committee

Originally based on this work: http://spamassassin.apache.org/presentations/macsysadmin_2009_presentation_final_post.pdf

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