Author Archive | Barry de Graaff

Are you using zen.spamhaus.org or dbl.spamhaus.org for fighting spam? Pay attention!

Spamhaus is making some changes in their policy enforcement, from their website: Are you currently using the Spamhaus Project’s DNS Blocklists (DNSBLs)? Do you access them via the Public Mirrors, for example, query “sbl.spamhaus.org” or “zen.spamhaus.org”? Do you use Cloudflare’s DNS? If you’ve answered “yes” to all three of those questions, you need to make […]

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Configuring Fail2Ban on Zimbra

This article is a how-to guide on installing Fail2Ban to block attacking hosts using a null route or blackhole routes. This can help mitigate brute force attacks on Zimbra. Especially brute force attacks on SMTP are very common. Prerequisite: It is required the OIP configuration must be done before configuring Fail2Ban service. For a Single-Server […]

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Nextcloud Talk Zimlet

Zimbra loves Nextcloud! And that is why Zimbra and Nextcloud work together to make both products integrate seamlessly. The Nextcloud Talk Zimlet add a button in the new appointment window that allows you to create a Nextcloud Talk meeting from the Zimbra Calendar. Screenshots Installing This Zimlet depends on the installation of Nextcloud Zimlet for […]

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Authentication Bypass in MailboxImportServlet vulnerability

Zimbra 8.8.15 patch 33 and Zimbra 9.0.0 patch 26 contain an important security update that fixes an authentication bypass in MailboxImportServlet (CVE-2022-37042 and CVE-2022-27925). If you are running a Zimbra version that is older than Zimbra 8.8.15 patch 33 or Zimbra 9.0.0 patch 26 you should update to the latest patch as soon as possible. […]

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Zimbra with Let’s Encrypt Certificates a step-by-step guide

This article is a step-by-step instruction on setting up a Zimbra with Let’s Encrypt certificates. If you are running a multi server installation of Zimbra it is recommended you set-up a dedicated VM for obtaining the Let’s Encrypt certificate and follow this blog. Prerequisites This guide assumes you are using Ubuntu 20 and you have […]

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Deprecation of the “X-XSS-Protection” header

Hello Zimbra Customers, Partners & Friends, In the past Zimbra recommended to set the X-XSS-Protection HTTP response header. This header used to enable additional protection against cross-site scripting (XSS) attacks in some web browsers. However this header is now deprecated and support is removed from most browsers. In case you have configured Zimbra to use […]

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