If you get an error like: Apr 15 12:41:03 webb4 postfix/sendmail[11234]: fatal: web1_user(12967): queue file write error in your mail log, then the value for message_size_limit in postfix main.cf is too low. Solve Postfix queue file write error Edit postfix main.cf: nano /etc/postfix/main.cf and set the message size limit to a higher value. E.g. message_size_limit ... Read more
When a server has more than one IP address, then postfix will use all IP addresses randomly to send out emails. This can cause your emails to be listed as SPAM on other servers because the sending IP does not match the reverse IP of the server hostname. The solution is to bind postfix to ... Read more
If you use postfix and / or amavisd-new on the mail server, you can use the following recipes to block emails with executable (exe, bat, scr) attachments. Block the attachments with a postfix header filter In ISPConfig, click on "Email in the upper menu, then on "Content filter" in the left menu and click on ... Read more
Sometimes you might have to work with the Spamassin Bayes Token database. This is the database that is used by the SpamAssassin Self Learning (Bayesian) Classifier to store the ham and spam tokens. This tutorial will show you how to make a backup of that database. E.g. when you want to move it to a ... Read more
NOTE: This post is about ISPConfig 3.0 and not 3.1 and newer. ISPConfig 3.1 and newer has DKIM support builtin, you can simply enable DKIM in ISPConfig 3.1 GUI now for the mail domain. DKIM is a system to verify the sender and integrity of emails. ISPConfig 3 uses amavisd-new as content filter for spam ... Read more
A copy of a incoming email can be sent to a second email address by adding a cc command to the "Custom Rules" field of the mailbox in ISPConfig. ISPConfig supports sieve as well as maildrop filter rules. The rule language depends on the LDA / POP3 / IMAP-Daemon that you use on your server. ... Read more
The following guide describes the steps to add DNS records that route emails from a domain managed in ISPConfig 3 to google apps / gmail. The guide assumes that you have already setup the dns zone for your domain in ispconfig. Login to ISPConfig, click on the DNS module icon in the upper navigation bar, ... Read more
The command below enables a stricter SPAM handling for postfix on ISPConfig 3 servers. In Detail: Reject sender hostnames with invalid syntax Reject sender hostnames that are no fully qualified domains (e.g. reject "server1" but allow server1.domain.tld) Reject sender domains that have no DNS records Check sender IP addresses against realtime blacklists. First make a ... Read more
As of ISPConfig 3.0.4, the text of the welcome email message that is sent to new email accounts is stored in the folder /usr/local/ispconfig/server/conf/mail/. The message has this format: ------------------------------------------------------------------------ From: ISPConfig <postmaster@localhost.localdomain> Subject: Welcome to your new email account. Welcome to your new email account. Your webmaster. ------------------------------------------------------------------------ The first line starts with "From: ... Read more
You might see the error: postfix/master[5309]: fatal: 0.0.0.0:smtps: Servname not supported for ai_socktype On a OpenSuSE server when you enable smtps in postfix master.cf file. The reason for the error is that the definition of the smtps port in /etc/services is missing. Solution Edit the /etc/services file vi /etc/services and add the following lines: smtps ... Read more