A null client is a machine that can only send mail. It receives no mail from the network, and it does not deliver any mail locally.

This setup is useful when you need to receive the output of your cron scripts.

[cc lang='bash']
\$ apt-get install postfix heirloom-mailx
\$ cat \< /etc/postfix/main.cf
myhostname = srv01.your-domain.com
inet_interfaces = loopback-only
mydestination =
EOF
\$ /etc/init.d/postfix restart
\$ netstat -tlnp | grep 25
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 31320/master

\$ echo "test" | mail -s "test" user@your-domain.com
\$ tail /var/log/mail.log
[/cc]