Re: Recognize mbox files?

[Alfred M\. Szmidt]

          A better idea would be for Rmail to detect whether it has
          already munged the file (a quick grep for "^X-RMAIL-.*"
          headers should do) and if not make the buffer read-only.

      That sounds like a good idea.  It should be enough to check the
      first message for that header, since a previous visit with Rmail
      will necessarily have displayed the first message and put that
      header into it.

   This mbox detection problem sounds like what we are trying to solve
   with bug#2222 (Labels). Launching rmail would automatically add a
   message on top of the mbox file, adding special rmail headers and
   thus making this mbox file detection really easy (if grepping for
   rmail headers on the first message). We would have solved two
   problems that way. I am strongly in favour of this approach. Still
   we need to find a consensus to the question: to hide or not to
   hide.

How would thiis work for "C-x C-f ~/RMAIL.foo"?  Is the suggestion to
do this check on all files one opens?  I think this would be very
bad...

Using file variables is the right solution.