Fancy Mail Splitting
--------------------

   If the rather simple, standard method for specifying how to split
mail doesn't allow you to do what you want, you can set
`nnmail-split-methods' to `nnmail-split-fancy'.  Then you can play with
the `nnmail-split-fancy' variable.

   Let's look at an example value of this variable first:

     ;; Messages from the mailer daemon are not crossposted to any of
     ;; the ordinary groups.  Warnings are put in a separate group
     ;; from real errors.
     (| ("from" mail (| ("subject" "warn.*" "mail.warning")
                        "mail.misc"))
        ;; Non-error messages are crossposted to all relevant
        ;; groups, but we don't crosspost between the group for the
        ;; (ding) list and the group for other (ding) related mail.
        (& (| (any "ding@ifi\\.uio\\.no" "ding.list")
              ("subject" "ding" "ding.misc"))
           ;; Other mailing lists...
           (any "procmail@informatik\\.rwth-aachen\\.de" "procmail.list")
           (any "SmartList@informatik\\.rwth-aachen\\.de" "SmartList.list")
           ;; People...
           (any "larsi@ifi\\.uio\\.no" "people.Lars Magne Ingebrigtsen"))
        ;; Unmatched mail goes to the catch all group.
        "misc.misc"))")

   This variable has the format of a "split".  A split is a (possibly)
recursive structure where each split may contain other splits.  Here are
the four possible split syntaxes:

"GROUP"
     If the split is a string, that will be taken as a group name.

"(FIELD VALUE SPLIT)"
     If the split is a list, and the first element is a string, then
     that means that if header FIELD (a regexp) contains VALUE (also a
     regexp), then store the message as specified by SPLIT.

"(| SPLIT...)"
     If the split is a list, and the first element is `|' (vertical
     bar), then process each SPLIT until one of them matches.  A SPLIT
     is said to match if it will cause the mail message to be stored in
     one or more groups.

"(& SPLIT...)"
     If the split is a list, and the first element is `&', then process
     all SPLITs in the list.

   In these splits, FIELD must match a complete field name.  VALUE must
match a complete word according to the fundamental mode syntax table.
You can use `.*' in the regexps to match partial field names or words.

   FIELD and VALUE can also be lisp symbols, in that case they are
expanded as specified by the variable `nnmail-split-abbrev-alist'.
This is an alist of cons cells, where the car of the cells contains the
key, and the cdr contains a string.

   `nnmail-split-fancy-syntax-table' is the syntax table in effect when
all this splitting is performed.