HOWTO Setup Nullmailer
From the authour's web-site: Nullmailer is a mail transport agent designed to only relay all its messages through a fixed set of "upstream" hosts. It is also designed to be secure.
Install Nullmailer
# emerge nullmailer -va
Configuration
Edit the following files to configure the machine to send mail to our mailing server (Bismarck).
/etc/nullmailer/adminaddr
admin@siat.sfu.ca
/etc/nullmailer/defaultdomain
iat.sfu.ca
/etc/nullmailer/me
$hostname.iat.sfu.ca
/etc/nullmailer/remotes
bismarck.iat.sfu.ca smtp