SpamAssassin is a long-running email spam filtering software that evaluates inbound email messages and scores the spaminess of them. SpamAssassin is the gold standard for spam scoring and filtering technology. This is largely due to the fact that the software is free for anyone to use (with proper license attribution) and is easy to customize the tests included in the scoring, as well as what score classifies a message as spam.
How Does SpamAssassin Score Emails?
SpamAssassin works by analyzing an email and giving it a spam score. The lower the score, the better the chances of the email getting delivered successfully. Conversely, the higher the score, the higher the likelihood the message is labeled spam/junk. A score below 5 is considered to be decent—above 5 means there is a good chance that the email will be filtered out somewhere before it reaches the inbox.
There are over 700 tests that SpamAssassin uses to detect spam, as well as a variety of analytical techniques. You don’t need to know all of the SpamAssassin tests, but it’s advantageous to understand how a SpamAssassin score is calculated. A score is given for each attribute SpamAssassin checks. These show the likelihood that the email is indeed spam. Individual attribute scores are added to give you your overall SpamAssassin score. For reference:
Negative numbers are great, as this indicates the email is unlikely to be spam and will keep your overall score down. “0” is neutral, meaning that this factor has little impact. Positive numbers suggest possible spam.
Low Scores Are Good
When mail server administrators or email providers are setting up SpamAssassin, they can pick their own SpamAssassin score threshold. The default score is 5, though the SpamAssassin team encourages people to set a score they feel comfortable with and lower it accordingly. Since administrators and email providers can put whatever value they see fit, it’s good to not settle for a score of 5 and be done. Some email services or administrators might set their threshold to 3, which means your email will be rejected and won’t arrive in their inbox.
For this reason, it’s important to aim for the lowest score possible. Aim for a score below 4, with your best bets lying between 0-2. Anything above 2 and you should be looking to fix whatever issues are causing tests to fail.
Negative Scores Are Ideal
So, now you know that a score between 0-2 is optimal, but what if your email score is negative? At first, seeing a negative value as a SpamAssassin test result might be confusing or alarming. However, negative SpamAssassin scores are exactly what you should strive to achieve, if possible, because: The lower the score, the better! The below image shows a snapshot of SpamAssassin scores received from a test email.