Hackers often install webshells on onpatched Zimbra systems and then wait for some time before actually abusing the compromised system. Especially on systems where critical security patches where installed too late, it may seem all was OK, where in fact a hacker has already gained access to the system, but did not do any other […]
Archive | Security & Privacy
Configure Zimbra OpenDKIM to sign the Subject header
By default Zimbra OpenDKIM does not sign the Subject header. At this time the configuration of what headers are signed by Zimbra OpenDKIM cannot be done via zmprov. There is a pending feature request to make these headers configurable via zmprov. In this article you will learn how to configure Zimbra OpenDKIM by customizing the […]
A Milter for using Spamhaus HBL with Zimbra Postfix
In this article you will learn how to use Spamhaus Hash Blocklist (HBL) to improve email protection in Zimbra. For a long time administrators of Zimbra have relied on Spamhaus to fight incoming spam by configuring Postfix using traditional blacklists. These traditional blocklists work by blocking IP (ranges) and domains of known spammers. When an […]
Improve email Zimbra protection with Spamhaus HBL
In this article you will learn how to use Spamhaus Hash Blocklist (HBL) to improve email protection in Zimbra. For a long time administrators of Zimbra have relied on Spamhaus to fight incoming spam by configuring Postfix using traditional blacklists. These traditional blocklists work by blocking IP (ranges) and domains of known spammers. When an […]
Optimizing Zimbra security and TLS settings via a script (updated May 2024)
By Barry de Graaff on February 8, 2023 in Product News, Community, Open Source, Partners, Security & Privacy, Zimbra SkillZ
A partner has requested a script to implement the Security tips and TLS settings documented at https://wiki.zimbra.com/wiki/Cipher_suites and https://wiki.zimbra.com/wiki/Secopstips . At Zimbra we love scripts! This article shows a script that configures Zimbra with strong TLS and security settings. Prerequisites You have set up a correct hostname and DNS, to check, run the following as […]
Zimbra Referrer-Policy best practice
By Barry de Graaff on February 1, 2023 in Product News, Did You Know, PowerTips – Admins, Security & Privacy
The “Referer” header is a HTTP header that is added by the web browser whenever a request is made. A Zimbra user who receives an email with links or images in the Zimbra web interface may unknowingly share information of the Zimbra server when clicking the link or viewing inline-images. For example when an email […]