Exim

Exim is a powerful and the most popular Mail Transfer Agent (MTA). It's reported to have a 57% market share. Also, Exim is the default MTA for Debian / Ubuntu.

Pre-installation
As only one MTA can be installed at the same time on a system, you might be required to unmerge an installed MTA. The package manager will report a block when another MTA is still installed. You can resolve this block by manually unmerging the old mail server. For example you can remove (which might have been installed as the default when a program requested a mail server to be installed) with this command:

Installation
Install :

Configuration
This configuration use spamassasin, clamav, postgresql and disallow open relay, you can adjust it to feet your needs.

Testing Exim
Once the configuration file is ready we can test the the file with the following command:

If everything goes right we can now start exim

Now we must be able to test how exim will route some addresses

Finally we can do the bunny test