How to Configure local.cf for SpamAssassin in 2026 As email threats evolve, ensuring your spam detection system is finely tuned is crucial. Apache SpamAssassin remains a powerful, open-source tool, but its effectiveness depends heavily on its configuration. In 2026, a well-tuned /etc/mail/spamassassin/local.cf (or /etc/spamassassin/local.cf on some systems) is the best way to reduce false positives and block modern spam.
This article provides a best-practice guide to configuring local.cf for optimal performance in 2026, focusing on security, scoring, and network tests. 1. Locating the Configuration File
SpamAssassin configuration files are usually loaded from /usr/share/spamassassin/ (default rules) and /etc/mail/spamassassin/ (local modifications). Primary Configuration File: /etc/mail/spamassassin/local.cf
Important: Local changes should always be made in local.cf, not in the default rules directory, to prevent them from being overwritten during updates. 2. Essential local.cf Settings for 2026
Open the file with root privileges (sudo nano /etc/mail/spamassassin/local.cf) and add or update the following settings. A. Basic Scoring & Thresholds
Set the required score to trigger spam detection. A score of 5.0 is the standard default, but you may want to lower it if you receive too much spam, or raise it if you see false positives. required_hits 5.0 report_safe 0 Use code with caution.
report_safe 0: This is crucial in 2026. It ensures spam is marked (e.g., modifying the subject) but not converted into an attachment, allowing for easier reviewing and training. B. Enabling Network Tests (Vital for Modern Spam)
Many spam threats in 2026 are identified via DNS-based blocklists (DNSBLs) and URI blacklists. skip_rbl_checks 0 use_razor2 1 use_pyzor 1 use_dcc 1 Use code with caution.
Razor/Pyzor/DCC: These are collaborative filtering networks. Ensure these packages are installed on your system. C. Configuring local.cf Scoring Overrides
If certain rules are too aggressive, you can adjust their scores in local.cf.
# Example: Reduce penalty for a rule that causes false positives score URIBL_BLOCKED 0.1 score HTML_IMAGE_RATIO_02 0.5 Use code with caution.
(Tip: If your local.cf is being overwritten by automated systems, consider creating a local-modified.cf file in the same directory, which is loaded after the main config). 3. Activating Necessary Plugins
Ensure essential plugins are active, particularly those dealing with modern phishing and spoofing.
loadplugin Mail::SpamAssassin::Plugin::SPF loadplugin Mail::SpamAssassin::Plugin::DKIM loadplugin Mail::SpamAssassin::Plugin::URIDNSBL Use code with caution. 4. Applying and Testing Changes
After editing local.cf, you must check for syntax errors and restart the SpamAssassin daemon.
Lint Test: Run the following command to check for errors. It should return no output. sudo spamassassin –lint -D Use code with caution. Restart Service:
sudo systemctl restart spamassassin # If using Amavis sudo systemctl restart amavis Use code with caution. 5. Best Practices for 2026
Keep Rules Updated: Regularly run sa-update to download the latest rule updates from the SpamAssassin community.
Use sa-learn: Train your system with known spam and ham (legitimate mail) to improve future detection.
Whitelist Trusted Sources: Add legitimate senders to your local.cf using whitelist_from to avoid false positives.
By tuning your local.cf with these settings, you ensure that your SpamAssassin installation remains a robust defense against modern email threats. If you’re interested, I can:
Explain how to set up Razor and Pyzor for better spam detection. Show you how to create a whitelist for trusted senders. Provide a sample local.cf file with recommended scores.
Let me know how you’d like to continue optimizing your email security. Conf – SpamAssassin configuration file
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