Increasing the number of simultaneous SASL authentication servers with Postfix

I had a customer complaining lately that messages sent via Gmail to one of my mail servers was occasionally receiving SMTP Authentication failures and bounce backs from Gmail. Fortunately he noticed it happening mainly when he sent a messages to multiple recipients and was able to send me some of the bounces for me to … Continue reading “Increasing the number of simultaneous SASL authentication servers with Postfix”

SpamAssassin + Postfix to Deliver Spam to an Alternate Mailbox

A fairly simple method of having postfix send messages through SpamAssassin, and then delivering the messages identified as spam to a separate mailbox: Configure SpamAssassin as normal in smtp inet n – – – – smtpd -o content_filter=spamassassin 2525 inet n – – – – smtpd -o content_filter=spamassassin spamassassin unix – n n – … Continue reading “SpamAssassin + Postfix to Deliver Spam to an Alternate Mailbox”

Vacation (AutoReply) Message with Virtual Users and Postfix

I’ve previously written about both Virtual Mail users, and about enabling vacation messages for postfix. The next step was to get vacation working with virtual users. My first thought was to try and make the sendmail ‘vacation’ program work with virtual users, but after digging into that a bit, it looked like more trouble than … Continue reading “Vacation (AutoReply) Message with Virtual Users and Postfix”

Postfix Vacation Message

The idea of a vacation message is kindof odd to me, but I had one client request it today, so took a look at configuring it. On RHEL/CentOS distros, the ‘vacation’ binary is distributed with sendmail, and is not available with postfix, so you have to build it yourself. Fortunately, it is about the easiest … Continue reading “Postfix Vacation Message”

Configuring Postfix SASL to authenticate against Courier Authlib

I ran across a system today that was using the VHCS control panel. It looks like the system wasn’t correctly configured to allow SMTP authentication. It uses Postfix as the MTA and Courier-IMAP for the Imap/POP3 server. It was populating the Courier-authentication database with email addresses and passwords to use for logging into the incoming … Continue reading “Configuring Postfix SASL to authenticate against Courier Authlib”

Postfix regexp tables are memory hogs

I spent a good part of the day today troubleshooting memory problems on some postfix mail servers. Each smtpd process was using over 11 MB of Ram which seems really high. Each concurrent SMTP session has its own smtpd process, and with over 150 concurrent connections, that was using well over 1.5 GB of Ram. … Continue reading “Postfix regexp tables are memory hogs”

A Case for Choosing Good Server Names

This morning, I had a client call me bright and early, frantic about some mail problems they were having.  All of their mail servers had stopped accepting incoming SMTP connections for some reason, and they couldn’t figure out why. After a little bit of investigation, I found that they were using postfix with MySQL-based virtual … Continue reading “A Case for Choosing Good Server Names”

Getting Dkimproxy Installed and Configured

Dkimproxy is a great program for getting Postfix to both sign and validate DomainKeys and DKIM messages. Prior to dkimproxy, one would have used dk-filter and dkim-filter which did DomainKeys and DKIM signing separately. dkimproxy is a newer version that combines the functionality into one program. Installing it can be a bit complicated because it … Continue reading “Getting Dkimproxy Installed and Configured”

CentOS Mail Toaster Guide Updated

I’m getting a chance to go through my own guide with several installations that I’m doing.  I noticed that PostfixAdmin has a new version 2.2.0 release available which changes the installation process significantly.   It is much simpler now and my howto guide has been updated to reflect the new changes.   Kudos to the developers who … Continue reading “CentOS Mail Toaster Guide Updated”

Converting mbox’s to maildir format

There is a handy utility for converting mbox style mailboxes into maildir format at To convert all of the mailboxes on your server: Edit /etc/sudoers and comment out the env_keep section. These variables make it so that the sudo command keeps some environment variables and tries to put things in the wrong directory. Download … Continue reading “Converting mbox’s to maildir format”