Dovecot

This should have lot more information on the Dovecot configuration.

Authentication SASL module

Dovecot runs a SASL module for authentication. To allow postfix (smtpd) to use that, it needs to set the socket in the private space of postfix, in /etc/dovecot.conf:

     client {
      # The client socket is generally safe to export to everyone. Typical use
      # is to export it to your SMTP server so it can do SMTP AUTH lookups
      # using it.
      #path = /var/run/dovecot/auth-client  #### OLD, changed by maurik 11/4/2014
      path = /var/spool/postfix/private/auth
      user=postfix
      group=postfix
      mode = 0660
    }

This was updated on 11/4/2014 by Maurik.