Movemail, nnmail (was mutt vs gnus)

[Sherilyn <sherilyn@suespammers.org>]

Simon Josefsson <jas@extundo.com> writes:

> Erwan David <erwan@rail.eu.org> writes:
> 
> > Simon Josefsson <jas@extundo.com> writes:
> >
> >> Erwan David <erwan@rail.eu.org> writes:
> >>
> >>>> Depending on the other MUA you're planning to use, you can choose a
> >>>> suitable Gnus backend. AFAIK, nnmaildir should even allow concurrent
> >>>> use of Gnus and other MUAs. Or use nnimap. nnfolder stores mail in
> >>>> standard Unix mailbox format, so you can read them with most Unix MUAs
> >>>> (but do _not_ write to them behind Gnus' back). 
> >>>
> >>>   So I cannot use /var/mail/$user
> >>
> >> Doesn't nnmbox:/var/mail/$user work?  Or nndoc:/var/mail/$user?  Some
> >> systems have maildirs in /var/mail, then nnmaildir:/var/mail/$user
> >> should work.
> >
> > No, since mail arrives in it, even when reading it. And I want to
> > *work* with it, ie. delete some messages, etc, which nndoc cannot do.
> 
> Ok.  If your system uses maildir it would work though, I think.
> Having several applications (possibly on different hosts) working on
> the same file seems to be asking for trouble.
> 
> Are POSIX file lock operations available in elisp?  I guess it would
> be possible to make this work.

The following is based on a brief scan of the emacs 20.7 source tree.

The way MUAs deal with this is generally to use a specialised movemail
program, which is supposed to deal with spool file locking properly.
Emacs comes with its own movemail, which is used, according to the
emacs 20.7 Debianized sourcei I just downloaded, by lisp/mail/rmail.el and
lisp/gnus/nnmail.el.  This is configured for the target system's locking
conventions and setuid/setgid requirements during emacs configuration
and installation.  pop3.el provides a POP-based alternative, but you'd
need to run a POP3 daemon to use that method.

When you do a nnmail-get-new-mail in Gnus, nnmail.el uses movemail
(you can define an external one if you don't like emacs' own) to move
email from the mail spool to a 'crashbox' from which the mail split,
if there is one, can be performed.

nnbabyl.el, nnfolder.el, nnmbox.el, nnmh.el and nnml.el all use the
nnmail-get-new-mail function.

See lib-src/movemail.c and the abovementioned lisp code.
-- 
Sherilyn
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