How to Reduce Your Score with SpamAssassin?
In our setup, we employ SpamAssassin as an anti-spam solution to evaluate our clients' email deliveries at Mailpro, both in terms of content and the email sender's reputation, including IP addresses.
The baseline score is 5, anything below that is considered legitimate, while anything above 5 is potentially problematic from an anti-spam perspective. The test provides an assessment, but it's not entirely reliable at 100% accuracy since not everyone uses this anti-spam tool, naturally.
To lower your score, you need to first understand how SpamAssassin operates:
SpamAssassin uses various filters and rules to detect unwanted or spam emails. These filters are designed to analyze different aspects of each email and assign a score based on suspicious criteria. If the total score exceeds a specific threshold, the email is categorized as spam. Here are some of the filters and rules commonly used by SpamAssassin:
1. Content-Based Filters:
- Keyword Detection: SpamAssassin looks for keywords and phrases commonly associated with spam, such as "free," "money," "promotion," etc.
- Text Analysis: The email content is scrutinized to detect poor grammar, excessive use of capital letters, special characters, etc.
- Suspicious Attachments: Attachments containing potentially harmful or unusual files can increase the score.
2. Header-Based Filters:
- "From" Header: Verification of the authenticity of the sender's email address.
- "Subject" Header: Analysis of the email subject to identify suspicious or misleading keywords.
- "Received" Header: Verification of the email's path through servers to detect anomalies.
3. Blacklist-Based Filters:
- IP Address Checking: SpamAssassin checks if the sender's IP address is listed in well-known spam blacklists.
4. Authentication-Based Filters:
- Avoid Using Free Email Addresses like gmail.com, yahoo.com, orange.fr, etc.
- SPF (Sender Policy Framework): Verification of the sender's authorization to send emails on behalf of the given domain.
- DKIM (DomainKeys Identified Mail): Verification of the validity of the email's DKIM signature.
- DMARC (Domain-based Message Authentication, Reporting, and Conformance): Utilizes SPF and DKIM to enhance email authentication.
5. MIME Header-Based Filters:
- Verification of the MIME header structure to detect anomalies.
6. Specific Rule-Based Filters:
- SpamAssassin uses specific rules that assign scores based on the detection of known spam patterns.
Each filter assigns a certain number of points based on its detection, and if the total score surpasses a predefined threshold (usually around 5 or 6 points), the email is classified as spam. Email server administrators can adjust this threshold as per their requirements.
Returning to the question of how to lower your SpamAssassin score, here are some recommendations:
- Refine Your Content: Avoid using typical spam keywords such as "free," "promotion," "easy money," etc. Ensure that the content of your email is coherent and well-written.
- Avoid Excessive HTML Markup (e.g., copying/pasting from Word, which may generate undesirable code): Refrain from using excessive HTML markup or suspicious links in your email.
- Do not use a standalone image, as it may be flagged as spam.
- Implement SPF, DKIM, and DMARC Authentication: Set up these authentication mechanisms to prove that the email is genuinely from your legitimate domain.
- Avoid Suspicious Mailing Lists: Steer clear of signing up for questionable mailing lists or purchasing unreliable email address lists.