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Increase your mail server security with Fail2ban

· 3 min read
Mauro D.

We are excited to announce a significant update to Stalwart Mail Server - the introduction of an integrated fail2ban-like system in our latest version, 0.5.3. This new feature marks an important advancement in our ongoing commitment to providing robust security measures for our users.

Understanding Fail2Ban

Before diving into the specifics of our new feature, let's revisit what Fail2Ban is. Commonly used in the world of server security, Fail2Ban is an intrusion prevention software that protects servers from brute-force attacks. It operates by monitoring server logs for suspicious activities, like repeated password failures, and responds by blocking the offending IP addresses, typically by updating firewall rules.

Tailored Security

In Stalwart Mail Server version 0.5.3, we've embraced the core philosophy of Fail2Ban but adapted it to better suit the unique environment of our mail server. Our integrated fail2ban system is designed to enhance security without relying on external Fail2Ban software. It's a part of Stalwart Mail Server, built directly into its architecture.

One key difference in our approach is how we handle the banning of IP addresses. Unlike traditional Fail2Ban that alters firewall rules, our system immediately drops further connections from any banned IP address. This swift action effectively cuts off malicious attempts at their source, ensuring immediate protection.

Fully Integrated

Another significant aspect of our fail2ban system is its integration across all mail server services. Whether it be JMAP, IMAP, SMTP, or ManageSieve, authentication failures in any of these services contribute to the ban threshold. This comprehensive coverage ensures that the security of one service is not compromised at the expense of another.

Advanced Tracking Beyond IP Addresses

A standout feature of our fail2ban system is its ability to track authentication failures not only by IP address but also by login name. This is particularly vital in defending against distributed brute-force attacks, where attackers might use numerous IP addresses to target a single account. Our system intelligently identifies such patterns and, after a certain number of failed attempts, blocks further authentication efforts for that account, regardless of the IP used. This means that an attacker cannot simply hop IP addresses to bypass security measures.


The introduction of this integrated fail2ban system in version 0.5.3 is a testament to our dedication to providing top-tier security for our users. This advanced security feature is meticulously designed to address and neutralize a wide array of cyber threats, especially sophisticated brute-force attacks.

We are proud to bring this new level of security to Stalwart Mail Server. This update reflects our ongoing commitment to adapting and evolving in the face of emerging cyber threats. With the integration of our fail2ban system, Stalwart Mail Server version 0.5.3 stands as a more secure, reliable, and resilient solution for your email server needs.

Stay tuned for more updates and features as we continue to enhance and refine Stalwart Mail Server. Your security is our priority, and we are dedicated to providing you with the best tools to protect it.