Splitting in Emacs 25

[Jarmo Hurri <jarmo.hurri@syk.fi>]

Greetings.

I upgraded my operating system, and along came Emacs 25. As a result my
gnus mail splitting stopped working.

Then I found this message:

https://lists.gnu.org/archive/html/bug-gnu-emacs/2015-07/msg00549.html

Basically the message (and thread) says that in Emacs 25, a number of
variables get reassigned to value nil somehow (?) after they have been
given a value by the user. These variables include nnimap-split-methods
and nnimap-inbox. I can verify that this happens also in my system
(Fedora 24 with Gnus v5.13).

So the author specified the splitting rules in (gnus-select-method). In
Emacs 24 you could define the rules by setting a value to
nnimap-split-methods anywhere.

Ok, so I tried to apply a similar strategy. I evaluated the following
while gnus was running:

(gnus-group-browse-foreign-server
      '(nnimap "mail"
               (nnimap-address "mail.myserver.com")
               (nnimap-server-port 993)
               (nnimap-stream ssl)
               (nnimap-inbox "INBOX")
               (nnimap-split-predicate "UNDELETED")
               (nnimap-split-crosspost nil)
               (nnimap-expunge t)
               (nnimap-split-methods
                '(
                  ("lists" "^To:.*xfce@xfce.org")
                  ("lists" "^To:.*users@lists.fedoraproject.org")
                  ("Spam" "^From:.*spamster")
                  ("personal" "")
                  ))))

This was probably I really bad idea. It _did_ apply the splitting
immediately after I subscribed my mail groups from the server. But after
restarting Emacs and Gnus weird things happened. For example, some
emails I sent to myself were completely lost. Gnus said it was splitting
mail, but the email just disappeared. Also, I could not find my split
rules in any save files, so they were probably not in effect.

What is the correct way to solve the problem? Is there, for example,
some hook where I could set nnimap-split-methods and nnimap-inbox so
that they would not be reset to nil after the hook?

Jarmo