Looking for 'hypermail' replacement

[Raul Miller <rdm@tad.micro.umn.edu>]

The best MUA I know of is the vm package for emacs.  

And, this is a very qualified "best" -- if your mail box is several
megabytes, and you want reasonable performance, you'll need a lot of
memory to run emacs in.  Also, you'll need to put something like:
(fset 'rmail 'vm) in ~/.emacs or
/usr/lib/emacs/site-lisp/site-start.el to prevent using a non mbox
format.

There are other options, both within emacs (gnus is an option, for
example) and without.

Out of curiosity, why is unix mailbox format so important?

-- 
Raul