postfix
postfix is a mail transport agent (MTA) designed to be a secure and easier to administer alternative to sendmail.
Handy configurations
In development environments (particularly in virtual machines) I like to be able to capture all email that is sent out. This is both handy because software that has embedded logic which emails production recipients can be caught, and also because emailing functionality can be tested without having to have a legitimate email recipient configured.
The following ultra-short configuration does just this, including a local aliases map which allows specific addresses to be redirected to different local users if desired:
alias_maps = hash:/etc/aliases inet_interfaces = loopback-only default_transport = local luser_relay = bjdean