Exim

exim is a mail transfer agent (MTA) originally developed by Philip Hazel at the University of Cambridge. It is widely adopted by Debian and related distros, but is targeted for all Unix-like systems. It has its own web page.

By default, Ubuntu 11.04 comes with exim4 as the default MTA for fresh installs.

Ubuntu Tips

 * There are several versions. I got the "simple" version, but that is not the only choice:
 * exim4 -- metapackage
 * exim4-base -- needed by all versions, and contains basic documentation.
 * exim4-daemon-light -- simple version
 * exim4-config -- configuration in /etc/exim4/conf.d, man pages and more.

Configuration

 * WARNING: the Debian web page (see External Links below) should be used in preference over the exim4 stuff, because they accord better with the Debian patches and file locations.
 * Warning: it may not work out of the box, so you should read the docs. There are
 * Files /usr/share/doc/exim4-base/README.Debian.gz and /usr/share/doc/exim4-base/README.Debian.html provided by package exim4-base.
 * If you install exim4-doc-html (optional), more complete web docs on your machine will be at file:///usr/share/doc/exim4-doc-html/html/index.html.
 * There is similar info documentation in the package exim4-doc-info.

Simple approach
One success story, on a 10.04 fresh install: /usr/sbin/dpkg-reconfigure exim4-config        ;and answer all questions; the documentation goes over each question in order and in detail.

/usr/sbin/update-exim4.conf --keepcomments     ; the argument is optional, but it may be best to keep the comments until you are very familiar with the package.

/etc/init.d/exim4 restart                      ; your mail should now be up and running. I hope your firewall and greylist daemon are in place already.

Provided By

 * exim.org
 * Patches by Debian

License
GPL

It would be nice to have contributions related to non-Ubuntu distros.