K9 is an experimental fork of the core Android POP/IMAP client. Primarily, K9 is focused on making it easy to chew through large volumes of email.

Changes:

EXCHANGE Fixed an authentication issue with WebDav support that caused by the last update. -ismarc31
Added support for scrolling on 2 of the screens in the account setup process to allow the full steps to be done in landscape mode. There are some graphical regressions in portrait mode from it that aren’t resolved yet. -ismarc31
EXCHANGE Removed display of path prefix. System now pulls all folders/subfolders. Does not display in a hierarchy, but will load messages from each folder. Only the final folder name is displayed instead of the path off of Inbox right now – ismarc31
EXCHANGE Added change to populate the url for the mailbox each time authentication occurs (url is in the response). Updated initial message population to use reverse order so initial display has newest first (only noticeable on slow connections). -ismarc31
Added the following 2 keyboard shortcuts in message list view: -baolongnt
S: Setttings
L: Last auto sync date time
Fixed bug # 122: Some keyboard shortcuts only work when a message is selected – baolongnt
fixed bug # 87: Acccounts all refresh at the same freqency – baolongnt
Fixed bug # 82: Messages lose their read status when getting new emails from POP3 server – baolongnt
FIxed bug # 81: Notifications never show up wen using POP3. – baolongnt
Added back auto-start of background message sync (most likely removed during merge) baolongnt

http://code.google.com/p/k9mail/