Sendmail Enabler is an application which allows you to configure sendmail in OS X with just one click. It also installs a POP3 server, which could allow you to run a fully-functioning mail server in minutes - if you've got the router, dns, firewall, port mapping, and all the rest of the stuff correct, of course ;-).
What's new in this version:
Added support for sendmail's Masquerade feature. Also, it now takes a look at sendmail's queues before it starts up sendmail. If necessary, it will create the queues and set their permissions correctly.