...if you need an MTA that can address any conceivable, and most inconceivable, possible circumstances.
\r\n\r\nOtherwise, what you're seeing: it's a fucking wild-ass complex behemoth described by a 1,000+ page manual (I've got a copy, if you need it, though several versions out of date), for which you need to learn the language an syntax of the macro code generator which understands the language and syntax of the configuration files to be able to tell it what to do.
\r\n\r\nExim, Postfix, or Courier are what today's technologically hip, but sensible, firm uses. Read all about it at [link|http://twiki.iwethey.org/twiki/bin/view/Main/MailServers|TWIT].