K9 Mail Android App is one of the best email clients for Android. It’s loaded with every email feature you could think of with the exception of ActiveSync (Push email, however IMAP integration syncs almost as fast as ActiveSync). K-9 Mail Android App is an open source email client for Android.

Includes multi-folder sync, email signatures, Bcc-to-self, return-address configuration, keyboard shortcuts, Exchange Support, message flagging, IMAP deletes, saving attachments, configurable notifications and more.

Here is the complete list of features:

Send and Receive
Configure to IMAP, POP3, and WebDAV (Exchange) email protocols
Search Multiple inboxes
Swipe for Previous/Next emails
Set Android Notifications, sounds and vibrate alerts
Delete email on the server works (A huge gripe with users of the default email client, when you specify to delete on the server… it doen’t, meaning double work when you do get back to desktop)
Signatures
Multi-folder Synchronization
Opening and Saving attachments
Email Sorting
Copy email text by Forwarding message
Frequency check sett