Re: rmail-default-file vs. (deleted) rmail-default-rmail-file

    > rmail files have always uppercase, so it makes it easy to list just
    > them with `ls *MAIL*'.  I find it also very confusing that `o' now
    > outputs to ~/xmail, when I have a ~/XMAIL that I use.

I have a habit of saving messages in files called xmail/foo.xmail, etc.,
all being lower case.  Since these file names are entered solely
by users, I think we cannot assume they all follow any rule.

But as regards ~/xmail vs ~/XMAIL for the default, ISTR that during
the transition to mbox format I saw an advantage in making the default
different.  But in fact the current Rmail deals just fine with saving
into Babyl files, so I now think it is better to keep the default
unchanged from Emacs 22.