I've been signed up to the Catalyst mailing list for years, and hardly ever read it. Gmail filters just fine, and if I ever need to search on something specific, it's dead easy. If I ever need to get rid of a mailing list, I unsubscribe and delete the label. Easy.
I find mailing lists usually tend to be better quality than web forums. That said, I recently asked some questions on Squid and Apache's mod_cache on the appropriate mailing lists, but they seemed to be a bit too "big picture" and were more or less ignored. It's those sorts of questions that tend to generate the most discussion on PerlMonks.