SpamAssassin
SpamAssassin is a powerful open-source tool designed to filter out spam emails. Developed by the Apache Software Foundation, it helps users manage…
How to block a domain in Zimbra
To block all emails from a specific domain in Zimbra, run the following commands as user zimbra (su – zimbra). To block…
How to disable Zimbra dnscache service
When you are using the Zimbra mail server behind NAT with Split DNS, you need to disable dnscache service. To view all…
How to Zimbra Split DNS with dnsmasq
When you install Zimbra on a server behind NAT, your public IP is not configured in the server, instead, it gets routed…
Fake SMTP Server for testing
When you develop a website or an application, you may need to use a fake SMTP server for debugging. Fake SMTP servers…
How to configure Hostname in PowerMTA
By default, PowerMTA uses the server’s hostname. You can specify a custom hostname per Virtual MTA. To set a hostname for VitualMTA,…
iRedMail Intentional policy rejection
On an iRedMail, when receiving an email from steam, the mail server rejects the email with the error message “Recipient address rejected:…
554 5.7.1 Unknown Sender in Local Domain
When sending an email from one server to another, the email gets bounced with an error SMTP error from remote mail server…
Google Workspace DKIM authentication settings failed.
When generating DKIM in google Google Workspace I got the following error message. DKIM authentication settings failed This error happens when you…
.forward file
Users can create a .forward file in their home directories that is used by mail servers like exim, sendmail used to redirect…
postfix smtp Must issue a STARTTLS command first
When sending an email to a server, mail bounced with the following error message. Action: failed Status: 5.7.0 Remote-MTA: dns; mail01.riedelbau.de Diagnostic-Code:…