Advanced Email Filtering System

Multi-layer defense against spam with SMTP-level rejection and intelligent content filtering

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🛡️ Multi-Layer Defense Against Unwanted Mail

CodaMail's sophisticated filtering system works at multiple levels to protect your inbox from spam, malware, and unwanted messages. What makes our approach unique is the level of control we give you at every stage of the filtering process. One size does not fit all when it comes to filtering!

Our system is designed to not just hide unwanted mail, but to actively discourage senders from continuing to target your address. This is achieved through our unique SMTP-level rejection system that makes blocked addresses appear completely non-existent to senders.

🚫 First Defense: Connection-Level Bot Protection & SMTP Rejection

Unlike most email services that merely sort spam into folders or silently discard it, CodaMail's first line of defense happens during the initial SMTP connection, before a message is even accepted:

🛡️ Anti-Bot Intelligence: We've collected data on spam bot behavior for decades and built a comprehensive identification system that blocks infected machine spam bots at the connection level
🛡️ User-Controlled SMTP Rejection: When you block a sender, domain, or top-level domain in CodaMail, it doesn't just disappear into a spam folder or get discarded, the sender receives an actual "User unknown" rejection during the SMTP handshake. Our server never even accepts the mail.
🛡️ Breaking the Spam Cycle: This rejection makes senders believe your address no longer exists, causing spammers to remove you from their lists (or someone you deliberately block to think that your account no longer exists). This is much better than them knowing it is a valid address and continuing to send mail that's merely hidden from your view.
🛡️ True Protocol-Level Control: Our system hooks each user's preferences directly into the SMTP protocol, giving you server-level control typically only available to system administrators

This connection-level control is crucial: other services might try global filters for everyone, but they may not be what you want. When you block something, other services just hide it from you, but the sender still thinks your address is valid, so you continue receiving unwanted mail that you just don't see. With our approach, senders are encouraged to remove you from their lists entirely.

🔍 Second Defense: Advanced Content Filtering

For non-encrypted received messages that pass the initial connection check, CodaMail employs sophisticated content analysis tools with unmatched user customization:

🛡️ Full SpamAssassin Control: We give you complete control over SpamAssassin, the industry-leading open-source anti-spam solution that analyzes message content, headers, and structure
🛡️ ClamAV Antivirus Protection: All messages are scanned for viruses, malware, and suspicious attachments
🛡️ Customizable Rules: Create your own spam rules based on content patterns, headers, or other message characteristics
🛡️ Choose which languages to mark as Spam: Choose which languages you accept mail in, marking any other as spam
🛡️ Bayesian Learning: Our system learns from your spam/not-spam classifications, automatically improving accuracy over time
🛡️ DNS Blocklist Integration: Leverage community-maintained reputation lists to identify known spam sources

Unlike most providers that hide these powerful tools behind simplified interfaces, we give you direct access to configure every aspect of content filtering to match your specific needs.

⚙️ Third Defense: Sieve Mail Filters

The final layer of defense consists of powerful mail filters that give you complete control over message processing:

🛡️ Comprehensive Sieve Filtering: Create sophisticated rules that process messages based on nearly any criteria
🛡️ Automatic Organization: Route messages to specific folders based on sender, subject, content, or other factors
🛡️ Conditional Actions: Set up complex if-then logic to handle messages differently based on multiple factors
🛡️ Header Modification: Add, remove, or change email headers for enhanced privacy or organization
🛡️ Automatic Responses: Configure auto-replies or vacation messages with detailed controls
🛡️ Zero-Access Encryption: You can add PGP-encrypt to any filter, too

For detailed instructions on setting up and managing these powerful filters, see our Understanding Sieve Email Filters guide.

🎆 Why Our Approach Is Different

Most email services treat spam filtering as something that happens after messages are received. They might hide spam in a separate folder or silently discard it, but the crucial difference is that the sender's system receives a successful delivery confirmation.

With CodaMail's approach, blocked senders receive an actual SMTP rejection with a "User unknown" error. This has several important advantages:

  1. Reduced Server Load: Rejected messages aren't processed by our spam scanning, content filtering, or storage systems
  2. Improved Deliverability: Since we reject unwanted mail early, our server reputation remains high, ensuring better delivery of legitimate messages
  3. Permanent Removal: Senders typically remove "non-existent" addresses from their lists, reducing overall spam volume over time
  4. Better Analytics: Since rejected connections don't count as "received then classified" spam, our spam metrics more accurately reflect the effectiveness of our filtering

This approach has helped us maintain clean, functional email service for decades, even for addresses that have been published on the web since the 1990s, like our helpdesk address.

🎆 Recommended Best Practices

  • Use Masked Aliases Strategically: Create different aliases for different purposes (shopping, newsletters, financial, etc.) so you can easily isolate and control specific types of mail
  • Start with Default Settings: Our default filter settings work well for most users; only adjust them if you're experiencing specific issues
  • Be Careful with TLD Blocking: When blocking a top-level domain, do not include a leading dot (e.g., use info not .info) to ensure proper filtering
  • Check Your Catch-All Settings: If you're missing expected emails, verify that your catch-all settings aren't set to reject all except listed addresses
  • Use "Stop Evaluating Rules": When creating Sieve filters, add the "Stop evaluating rules" action as the final step in most filters to prevent unexpected interactions between filters
  • Regularly Review Your Filters: Periodically check your filter configurations to ensure they're still working as expected

🚑 Need Help?

If you're experiencing issues with spam or need help configuring your filters, our support team is here to help. We've been fighting spam and protecting email privacy for a very long time, and we're happy to share our expertise.

Contact our helpdesk at helpdesk@codamail.com with any questions or check our FAQ for more information.