Unix program that sends email directly using MX record

[Dan]

Kelly Jones(kelly.terry.jones at gmail.com)@2008.11.22 14:16:56 -0700:
> What Unix program sends email directly, using the MX record of the
> recipient, instead of using sendmail or an installed MTA?

Sendmail/Sendwhale sucks for just about anything. There are much better
MTAs out there. For your needs, I think 'nullmailer' from Bruce Guenter
 would fit the bill and so would qmail in nullmailer mode. Postfix as well.