Exim

Vademecum

apt-get install exim4
dpkg-reconfigure exim4-config    # choose "internet site;"
ln -s /etc/init.d/exim4 /srv/config/init.d/
ln -s ../../../init.d/exim4 /srv/config/this/init.d/S20_exim
ln -s ../../../init.d/exim4 /srv/config/this/init.d/K80_exim

Config

From Setting Up Your System To Use E-Mail

As mentioned earlier, the installed Debian system is only set up to handle e-mail local to the system, not for sending mail to others nor for receiving mail from others.

[...]

If you would like your system to also handle external e-mail, you will need to reconfigure the exim4 package[26]:

# dpkg-reconfigure exim4-config

Remember to

• choose 'internet site; mail is sent and received directly using SMTP'
• list for all incoming 'IP-addresses to listen on for incoming SMTP connections' leaving the box blank
• set an A and MX record on your DNS provider to deliver your mail for your server:

mail.campisano.org.	CNAME	IN	300	campisano.org
campisano.org.		MX	IN	300	mail.campisano.org

NOTE: edit /etc/default/exim4 if you don't want exim listening on port 25:

QUEUERUNNER='queueonly'