xmailer looks like a good mail solution, but it's loaded with features
I do not need. I will try xmailer in another project ;-)
Well, NAT'ing is okay, but some people don't like their mailservers to
be exposed to the world in any way.
I'll take a look at ssmtp.
So far, I've found "spammer deterrent" from http://sd.inodes.org/ . It
has some anti-spam features but it's lightweight.