Here last 100 rows of my /var/log/maillog log file
Dec 12 09:26:16 kines postfix/master[3682]: warning: /usr/libexec/postfix/cleanup: bad command startup -- throttling Dec 12 09:26:42 kines postfix/smtpd[8938]: fatal: unsupported dictionary type: mysql Dec 12 09:26:43 kines postfix/master[3682]: warning: process /usr/libexec/postfix/smtpd pid 8938 exit status 1 Dec 12 09:26:43 kines postfix/master[3682]: warning: /usr/libexec/postfix/smtpd: bad command startup -- throttling Dec 12 09:27:10 kines postfix/pickup[8891]: fatal: watchdog timeout
<big snip>
Your postfix does not support mysql. It needs to be rebuilt with mysql support. If this is a source tarball installation, you need to recompile it. If you are using centos postfix packages, you need to pick up the postfix package in the plus repository which I believe has mysql support.
Dec 12 09:40:57 kines dovecot-auth: MySQL: Can't connect to database postfix: Can't connect to local MySQL server through socket '/var/tmp/mysql.sock' (2) Dec 12 08:40:57 kines imap-login: Disconnected [127.0.0.1]
Centos/RHEL mysql sockets are normally /var/lib/mysql/mysql.sock
After a reboot, things become more complicated... New errors...
I need to learn how to setup this kind of software, I know...
You need a bit more than just learn how to setup...you need to understand how the whole thing works.