Dovecot dead but subsys locked error

When you restart dovecot, if it won’t start up again it’s likely the process crashed on startup but left the subsys lockfile in place. This prevents dovecot from starting up again. If you run /etc/init.d/dovecot status and get the error message "dovecot dead but subsys locked" then you have this problem.

Spamassassion connection refused

If you get a message like the one following, then you are filtering emails through spamassasin using /usr/bin/spamc but the spamassassin service is not running. connect(AF_INET) to spamd at failed, retrying (#1 of 3): Connection refused.

Updating Postfix’s virtual alias maps

Postfix allows you to store virtual alias maps in a text file, which tells postfix how to route virtual email addresses to real users on the system. This setting and the file location is determined in the postfix configuration file /etc/postfix/ like so:

virtual_alias_maps = hash:/etc/postfix/virtual

Postfix “file too large” error message

Running postfix on a CentOS mail server I got the following error message both in a returned email and also in the log file: "cannot update mailbox … error writing message: File too large". This post looks at the erorr message in the bounce email, the log files, and the solution to the error. This error will also affect postfix mail servers on Red Hat Enterprise Linux and probably other default installs of Postfix as well.