SpamAssassin is an application that test email messages in order to see if they are defined as spam or not. It performs hundreds of tests on the messages and will assign a score to the message. This score can then be used by applications in order to filter emails so that only the relevant messages get through to the user. The following article briefly lists the tests run by SpamAssassin, explains how to lower your spam score and avoid false positives, and also aids in understanding the Spam scores.

How does SpamAssassin determine that email is spam?

SpamAssassin checks many variables within an email in order to determine the spam score. A user can also change the settings that SpamAssassin uses in order to determine if an email will score as a spam or not. SpamAssassin settings can be changed within the cPanel. The number and complexity of the tests are so numerous that it can be difficult to understand why an email was given a particular score. If you want to see the tests being run using the latest version of SpamAssasin, go to:

SpamAssassin Tests Performed (version3.3.x)

(for older versions of SpamAssassin, see older versions of SpamAssassin)

How to Lower Your SpamAssassin Score

The main thing is to make sure that your email does not fall into the definition of being spam. Here are some common issues and items to include in your email as defined by the CAN-SPAM Act of 2003 (section 5):

  • False or misleading information in the header
  • False or misleading information in the subject line
  • Provide indication that email is an advertisement
  • Include a type of return email address that allows recipient to opt-out
  • Email includes a clear notice that there is an option to opt out
  • Email is not sent after a recipient had sent notice that they wish to no longer receive the email
  • Email contains a valid, physical address.

Other great sources of information that would help to keep your email from being labeled as spam or generating a false positive result includes:

Another option to help in keeping your email from being labeled as spam is to use Domain Keys. The Domain Key is an e-mail authentication system that allows for incoming mail to be checked against the server it was sent from to verify that the mail has not been modified. This verifies that the email is coming from the listed sender and allows abusive messages to be tracked with more ease.

Understanding X-Spam scores

Reading the X-Spam scores in the header of an email can definitely appear to be difficult. When you become familiar with the sections of the header, it becomes much easier to identify the portions that deal with SpamAssassin. Here are some of the headers that will give you information on how SpamAssassin judged the email:

X-Spam-Score This is the numerical value assigned to the email by SpamAssassin based on it rated the email to be possibly spam. Generally, the higher the number, the more that it is considered spam. The lower the number, the more that is considered a legitimate email or not spam.
X-Spam-Flag This is typically either YES or NO; generally, a YES will indicate a SPAM message and NO a non-spam message.
X-Spam-Report This report will typically either give an explanation of the spam identification provide a summary of the flags that the message triggered that mark it as spam
X-Spam-Bar This will either be a "-" indicating a non-spam email, or a number of "+" signs indicating how strongly SpamAssassin identified the email as spam.
X-Spam-Status This is visible when a mail client is configured to show full headers. Can also contain a yes/no value indicating if it is spam, total score for the message, score required for message to be classes as spam, version of SpamAssassin used. For the complete list, go to definition of X-Spam-Status

Click on the following examples of a non-spam email header with SpamAssassin and an email identified as spam by SpamAssassin.

Email not marked as spamEmail marked as spam
Mail not detected as spam Mail detected as spam
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