cy@
Developer
I think the minimalist dma is probably the best approach (see my comments below about my philosophy). People who want something a little more feature rich should choose one of the ports (postfix, exim, sendmail, or one of the others).So? The major point is, base doesn't need a full-featured MTA, it just needs a tiny one with the most basic features (like local delivery and relaying to a "smarthost"). Or would you want Postfix or Exim to replace Sendmail in base? Would make little sense.
For all those who prefer sendmail, there's always mail/sendmail.
Personally, I use postfix. I've used it on my exterior gateway for a couple of decades and have switched all my machines, except one, to it this calendar year, with the last one running the sendmail port because I feel I should keep one sendmail machine around just to keep my hands dirty with it.
Regarding my base O/S philosophy, everything server-like except for the absolute essentials such as sshd should be moved to ports. This includes moving KRB5 KDC, ntp, full featured MTA (keeping dma), telnetd, ftpd, and all other daemons not needed for initial system setup, all moved to ports. People should be able to pick and choose what they want to run on their machines.