K-9 Mail

K-9 Mail is an open-source mail client for Android. It boasts a very impressive functionality and support for various protocols.

Key features

• Manage multiple accounts at once;
• Mail search across all accounts;
• IMAP, POP3 and Exchange 2003/2007 support (with WebDAV);
• support for IMAP push email;
• adding signatures;
• email marking;
• folder synchronization;
• PGP/MIME support.