I'm not one of the developers and this is a totally unprompted recommendation, but, if you haven't tried it, I can't say enough good things about the Claws Mail client. It's an extended version of Sylpheed, I think, and is the only graphical (Gtk) mail program I've found that comes anywhere near to Mutt.
Unlike Evolution, it does only one thing, but it does that one thing--mail handling--very, very well indeed. Plugins are available to handle PGP in all its various permutations; to read PDFs inline; there's even a Perl plugin that allows you to script actions that can't be configured natively, though what those may be I can't imagine.
If you're looking for a mail client that can chew through a large number of mailing lists, do check it out: threaded indexing (à la Mutt), handles quote levels in contrasting colors (like Mutt), and is set up for easy pre- and post-processing of mails. It's also fast--much faster than Evolution. (I have to admit that even as a Nat and Miguel fanboi.)
I still use Mutt to read mail on the server, but when I'm on my Fedora box, Claws Mail is just so good I just had to share.
(Be sure to get the claws-mail-plugins RPM if you try it out.)
JL