Using gnus with locally stored email (repost from users ml)

[Gary <gnus@garydjones.name>]

Sorry, I know this isn't the right place really, but I asked on the
users ml and didn't really get where I am trying to get to.

I've got a whole pile of locally stored mail in mbox files in ~/Mail and
subdirectories thereof. Mutt is pretty easily configured to handle that,
and that's what I used exclusively until a few months ago. I'm not
married to mbox, I could also use maildir or any other format that mutt
and gnus are both capable of reading.

As I've been moving ever more to emacs, I find myself using gnus more
and more, but haven't tried integrating locally stored email (for which
I still use fetchmail & procmail). What's my best way of doing that? I
still want to suck some email down to my own HD, and that's not going to
change, so please don't suggest using imap :)

If I can, I would still like the email to be accessible to mutt, even if
I only rarely use it. Would nnfolder screw that up? Otherwise, that
looks like the closest to what I already have, right?

Or do I want
  (setq mail-sources
        '((directory :path "/home/gary/Mail")))

Actually I tried just that, and nothing happened, so I guess I have to
also set something else? I'm rather confused about the
relationship/differences between mail sources and backends...