Email, RSS and newsgroup client with integrated spam filter

 Thunderbird is a full-featured email, RSS and newsgroup client that makes
 emailing safer, faster and easier than ever before. It supports different mail
 accounts (POP, IMAP, Gmail), has a simple mail account setup wizard, one-
 click address book, tabbed interface, an integrated learning spam filter,
 advanced search and indexing capabilities, and offers easy organization
 of mails with tagging and virtual folders. It also features unrivalled
 extensibility.