dot (.) in mail group names?

[Michal Jankowski <Michal.Jankowski@fuw.edu.pl>]

I'm trying to have a hierarchy of mail groups.
So I have procmail sorting mail into something like:

~/incoming/a.b.c.spool
~/incoming/a.b.d.spool

etc, and then use
 '(gnus-secondary-select-methods (quote ((nnfolder "ccfs1.fuw.edu.pl"))))
 '(mail-sources (quote ((directory :path "~/incoming/"))))

and it __almost__ works.

That is, it works if I do "mkdir -p ~/Mail/a/b" before starting emacs,
but doesn't work otherwise. A truss of emacs shows it doing 
mkdir("~/Mail/a", 0777)           = 0
mkdir("~/Mail/a/b", 0777)         = 0
but perhaps it happens too late to work properly.

I'm using emacs-20.4 and gnus 5.8.2.

Thanks
  Michal