Trillian is a proprietary multiprotocol instant messaging application.

Yandex.Mail is a free email service.

Kopano is an open-source groupware application suite originally based on Zarafa.

K-9 Mail is an open source email client with support for multiple accounts, search, IMAP push email, multi-folder sync, flagging, filing, signatures.

FastMail is an email service offering paid email accounts for individuals and organizations.

ALTO Mail is a smart take on email that makes organizing real life easy.