Mail Clients
Mail Client :
An email client (or mail user agent [MUA]) is a computer program that is used to read and send e-mail. Protocols supported by email clients include POP3 and IMAP. IMAP and the updated IMAP4 are optimized for storage of e-mail on the server, while the POP3 protocol generally assumes that the e-mail is downloaded to the client. The SMTP protocol is used by most email clients to send e-mail.
From :en.wikipedia.org/wiki/Mail_client
An email client (or mail user agent [MUA]) is a computer program that is used to read and send e-mail. Protocols supported by email clients include POP3 and IMAP. IMAP and the updated IMAP4 are optimized for storage of e-mail on the server, while the POP3 protocol generally assumes that the e-mail is downloaded to the client. The SMTP protocol is used by most email clients to send e-mail.
From :en.wikipedia.org/wiki/Mail_client
7 products available, Sorted alphabetically
ActiveJMS
Active JMS is 'Open Source ActiveX Java Message Service Client API'. ActiveJMS offers a freely available, non-proprietary, open .....
Platform : MS Windows
Active JMS is 'Open Source ActiveX Java Message Service Client API'. ActiveJMS offers a freely available, non-proprietary, open .....
Aethera
Aethera is a pim application, i.e. it handles all kinds of personal information: email, contacts, notes, tasks, todos, journals. I .....
Platform : Linux, Win32, Mac OSX
Aethera is a pim application, i.e. it handles all kinds of personal information: email, contacts, notes, tasks, todos, journals. I .....
Apache jSieve
jSieve is a Java implementation of the Sieve mail filtering language defined by RFC 3028. jSieve is implemented as a langauge proc .....
Platform : Java
jSieve is a Java implementation of the Sieve mail filtering language defined by RFC 3028. jSieve is implemented as a langauge proc .....
Mahogany
Mahogany is an OpenSource cross-platform mail and news client. It is available for X11/Unix and MS Win32 platforms, supporting a w .....
Platform : Unix, Windows
Mahogany is an OpenSource cross-platform mail and news client. It is available for X11/Unix and MS Win32 platforms, supporting a w .....
MHonArc
MHonArc is a Perl mail-to-HTML converter. MHonArc provides HTML mail archiving with index, mail thread linking, etc; plus other ca .....
Platform : Perl Application
MHonArc is a Perl mail-to-HTML converter. MHonArc provides HTML mail archiving with index, mail thread linking, etc; plus other ca .....
Mutt
Mutt is a small but very powerful text-based mail client for Unix operating systems. .....
Platform : Unix like
Mutt is a small but very powerful text-based mail client for Unix operating systems. .....
SeaMonkey
SeaMonkey is a Web-browser, advanced e-mail and newsgroup client, IRC chat client, and HTML editing made simple -- all your Intern .....
Platform : Mac OSX
SeaMonkey is a Web-browser, advanced e-mail and newsgroup client, IRC chat client, and HTML editing made simple -- all your Intern .....
Reference Links

Groupware, Messaging