Thunderbird

Website/Download: http://mozillamessaging.com/thunderbird
License: Freeware
OS: Windows Mac Linux
Latest Version: 2
Publisher's description:
Mozilla Thunderbird is a free, open source, cross-platform e-mail and news client developed by the Mozilla Foundation. Thunderbird can manage multiple e-mail, newsgroup and RSS accounts and supports multiple identities within accounts. Features like quick search, saved search folders, advanced message filtering, message grouping, and labels can help manage and find messages.