Re: Recognize mbox files?

["Alfred M\. Szmidt" <ams@gnu.org>]

   >> >> Otherwise, Rmail will have to be considered risky for use by mail
   >> >> admins.
   >> > Heh, what it does nowadays is nothing compared with what it did before
   >> > the mbox merge: it would convert the file to Babyl!  How's that for
   >> > ``risky''?
   >> 
   >> But *when* did it do it?  Would it do it, just by C-x C-f <somemboxfile> RET?

   > The conversion happened when you turned on rmail-mode.  If C-x C-f did
   > that automatically, the conversion happened automatically just by
   > typing C-x C-f.

   But could C-x C-f do that "by accident"?  Anyway, even if it could, we
   want to be more careful now.  I think the idea of checking the presence
   of RMAIL tags before allowing to modify the buffer is a good plan.

There seems to be confusion about how rmail work(s/ed).

A RMAIL/BABYL file contains a header that specifies the mode of the
file, so when you open such files (C-x C-f), you will get the file in
rmail-mode.

If you opened a random mbox file, no conversion occurs. 

If you type M-x rmail, rmail will read the mail spool, and save the
content to ~/RMAIL, converting the result to BABYL.

When a buffer was converted to BABYL, the file was never saved
automatically.  This was, I found anyway, useful for looking at mbox
files where you could then just use rmail to navigate th file,
disgarding the conversion later.

rmail would _never_ convert a file to BABYL unless the user explicitly
commanded emacs to do so, by invoking M-x rmail, or C-u M-x rmail.


Infact, a solution to the whole problem is simple.  Upon adding
headers, add the following header to the first message:

X-RMAIL-MODE: -*- rmail -*-

The file will then be handled by Emacs correctly, when the user does a
C-x C-f.