KMail is a fully-featured email client that fits nicely into the K Desktop Environment, KDE. It has features such as support for filters, PGP/GnuPG privacy, inline attachments, drag and drop support of messages and attachments and support for multiple pop accounts. Read more hot
Empath is the name of a set of mail client support libraries and kparts which provide a complete framework for implementing a modular, standards-compliant, efficient, safe, flexible mail client.
Kiltdown is an open source E-Mail program that has been tested under Linux (RedHat and SuSE), FreeBSD 3.4 and 4.1, and Solaris 8/Intel. It supports most features that you'd expect in a mail program, such as MIME attachments, address books, Reply All, etc.
KImap is an E-Mail Client with KDE look and feel and support for the following protocols: IMAP, POP3, MH, NNTP & Unix-Style mailfolders.
Liamail is a graphical email client written with the QT libraries. Liamail is like Outlook Express. This email client supports attachment now with library mimepp. Protocol supported are POP3 and SMTP.