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:

code renamed to ease merging – jessev Added silent ‘ongoing’ notification when checking email – baolongnt New email notification now includes purple blinking LED – baolongnt More reliable background sync by using wake lock –> Background sync now work even when the device is asleep (Thanks danapple0) – baolongnt Added about dialog. – young.bradley Update the domain validator to accept ip addresses and “localhost” – young.bradley block server entries in AccountSetupIncoming.java and AccountSetupOutgoing.java that are not valid domain names. – young.bradley Update for folders to display the “path” that the folder resides in (ie, Inbox/Work/To Me) rather than just the name of the folder. Allows an easier understanding of the hierarchy until true folder trees can be implemented. – ismarc31

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