Claws Mail - Email Client and News Reader Based on GTK+
Claws Mail is a GTK+ based, lightweight, and fast e-mail client and newsreader. Supports POP3, APOP, IMAP, SMTP, SMTP AUTH, NNTP, LDAP, multiple accounts, spell-checking, addressbook, SSL, GPG, filtering, i18n, & more. It is further extended by plugins. Lots of extra functionality, like an RSS aggregator, calendar, or laptop LED handling, are provided by extra plugins.