The showstopper missing feature which has so far prevented me from switching to
Mutt from Pine:

Pine can be configured with an arbitrary command for accessing an IMAP server,
for example 'ssh <mailhost> exec /usr/sbin/imapd', and then use stdin and stdout
of that command. 

Mutt can't do that, AFAICT. All it can do is run a separate command _before_
trying to connect as normal with TCP.