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 …

Architectural Design Reference for Large Zimbra Deployments in Amazon Web Services

This post documents a high-level architectural design reference for hosting large Zimbra deployments in Amazon Web Services cost-effectively, with a high degree of security, performance, redundancy and resiliency — and with very short RPO (Recovery Point Objective) and RTO (Recovery Time Objectives) targets. For single-server installations, you can still use …