I've decided to use Claws Mail because it looked pretty good and mainly because I respect Adam Gomaa's opinion a lot. My first customization is to change the default directory used to store the messages. I couldn't find this in the documentation, but found the solution after Googling. The solution is: edit the path in your ~/.claws-mail/folderlist.xml file. Now to figure out how to show new message notifications in my wmii status bar!
aws
(4)
bison_flex
(1)
blogger
(4)
c
(10)
cardstore
(5)
colinux
(2)
concurrency
(8)
conkeror
(2)
cygwin
(17)
dell
(3)
django
(31)
eclipse
(30)
emacs
(18)
email
(1)
error
(11)
gnip
(1)
json
(1)
keyboard
(3)
linux
(31)
matplotlib
(5)
mercurial
(3)
openid
(1)
personal
(4)
preferences
(4)
pyqt
(18)
python
(88)
rails
(1)
ratpoison
(3)
recursion
(1)
rsync
(3)
ruby
(2)
sql
(10)
subversion
(4)
twisted
(5)
ubuntu
(33)
untagged
(7)
urxvt
(3)
vxworks
(26)
wmii
(3)