This variable can also have a function as its value, the function will
be called with the headers narrowed and should return a group where it
-thinks the article should be splitted to.
+thinks the article should be splitted to. See @code{nnimap-split-fancy}.
The splitting code tries to create mailboxes if it need too.
+To allow for different split rules on different virtual servers, and
+even different split rules in different inboxes on the same server,
+the syntax of this variable have been extended along the lines of:
+
+@lisp
+(setq nnimap-split-rule
+ '(("my1server" (".*" (("ding" "ding@@gnus.org")
+ ("junk" "From:.*Simon")))
+ ("my2server" ("INBOX" nnimap-split-fancy))
+ ("my[34]server" (".*" (("private" "To:.*Simon")
+ ("junk" my-junk-func)))))
+@end lisp
+
+The virtual server name is in fact a regexp, so that the same rules
+may apply to several servers. In the example, the servers
+@code{my3server} and @code{my4server} both use the same rules.
+Similarly, the inbox string is also a regexp. The actual splitting
+rules are as before, either a function, or a list with group/regexp or
+group/function elements.
+
Nnmail equivalent: @code{nnmail-split-methods}.
@item nnimap-split-predicate