Archive backends

[Marcin 'Qrczak' Kowalczyk]

How to use nnml as the backend for sent mails folder? I can't use
nnfolder for all of them because "Buffer exceeds maximum size"
(Emacs doesn't seem to handle files over 130MB), and manually moving
sent mail to another folder from time to time is silly.

BTW, the interface for customizing gnus-summary-archive-group is buggy.
If I set it to *expression* ((if (message-news-p) "sent-news" "sent-mail"))
then, after opening the customize interface, it shows up as *function*
((if (message-news-p) "sent-news" "sent-mail")) and can't be updated
without manual copying & pasting it into the *expression* variant.

-- 
   __("<         Marcin Kowalczyk
   \__/       qrczak@knm.org.pl
    ^^     http://qrnik.knm.org.pl/~qrczak/