Zimbra Fail2Ban Best Practices – Updated for 2024

This post contains our current Zimbra Fail2Ban Best Practices and will show you how to configure Fail2Ban optimally on your Zimbra servers. Bad actors, overly aggressive marketing companies and others clog up our Inboxes with unwanted emails, and increase the load on our Zimbra servers. While Fail2Ban will effectively block …

Host Your MTA-STS Text File on Amazon Web Services For Pennies Per Month

We know that deploying MTA-STS better secures inbound email and can prevent MITM and downgrade attacks. But you need a public web server to host the ~/.well-known/mta-sts.txt file.  Not everyone has access to a web server they can use for this purpose, and even if they did, securing, patching, monitoring …

Zimbra Security Tip – Regulate Outbound Traffic With Stateful Firewalls

Historically, Zimbra firewalling has focused on regulating only Inbound traffic, but we can better protect our Zimbra systems if we also regulate Outbound traffic by using a Stateful Firewall. What Is a Stateful Firewall? Stateful firewalls, which now account for the majority of SMB and enterprise grade firewalls, can track …

Secure Your Zimbra Distribution Lists From Bad Actors

Zimbra’s Distribution Lists are widely deployed on account of their powerful productivity-enhancing features, but in a default Zimbra installation, anyone anywhere can send email to any of your distribution lists — lists like “everyone@mycompany.com” are particularly ripe for exploitation by bad actors.  This post will show you how to secure your …

Zimbra Selective Postfix Rate Limiting To Improve Email Deliverability

In this post, we’ll show you how doing selective Postfix rate limiting will improve your Zimbra system’s email deliverability. Various trade press accounts have reported that COVID resulted in email volumes essentially doubling.  For large email providers, especially the free email providers like Gmail, Yahoo and Outlook.com, they have had …

How To Defend Zimbra Against Distributed Brute Force Login Attacks

Increasingly we are seeing distributed brute force login attacks on our Zimbra hosting environment, as well as on our on-premises customers’ Zimbra systems. These login attempts typically come from 10 to 20 or so different IP addresses from around the globe, and are infrequent enough that Zimbra’s Denial of Service …