instant mail

Claws Mail is a GTK+ based, lightweight, and fast e-mail client and newsreader.

Opt-In Mail is a small application to send e-mail.

Vivian Mail - A free mail client for SMTP and POP3-Server.

Smart Mail Notifier is a tiny user friendly software for checking mail and RSS

Send your mail through http proxy but not only the mail proxy

Receive notifications from POP3 or IMAP4 e-mail enabled account to your Windows desktop.

Manage multiple e-mail accounts in one program.

Mokum Mail: EMail Checker / Reader, HTML EMailer and WEB Browser, all in one!

Koma-Mail is an email client which is very comfortable+has many useful functions

Revolver Mail is an email client, an address book and a calendar.