K-9 Mail

K-9 Mail is an open source email client with support for multiple accounts, search, IMAP push email, multi-folder sync, flagging, filing, signatures, BCC-self, PGP/MIME & more! K-9 supports IMAP, POP3 and Exchange 2003/2007 (with WebDAV). Install the app "OpenKeychain: Easy PGP" to encrypt/decrypt your emails using OpenPGP. K-9 is a community developed project.