Configuring authentication for outbound e-mail

With our current mail server setup, we can retrieve e-mail remotely and we can send mail from the local box, but we cannot send mail from remote systems. In order to enable this functionality, we need to configure Postfix to require auth for sending outbound mail from remote users. Typically, this requires setting up a SASL server of some variety like Cyrus saslauthd. In our case, we're going to use Dovecot's built in SASL server.

How to do it…

1. Configure Dovecot to expose its SASL interface to Postfix by editing /etc/dovecot/conf.d/10-master.conf:

   service auth {
   …
     unix_listener /var/spool/postfix/private/auth {
       group = postfix
       mode = 0660
       user = postfix
     }
   …
   }

2. Configure Postfix to authenticate via SASL by editing master.cf and adding:

   submission inet n - n - - smtpd
     -o smtpd_tls_security_level=encrypt
     -o smtpd_sasl_auth_enable=yes
     -o smtpd_sasl_type=dovecot
     -o smtpd_sasl_path=private/auth
     -o smtpd_sasl_security_options=noanonymous...