Mozilla Thunderbird is a free, open source, cross-platform e-mail and news client developed by the Mozilla Foundation. Thunderbird aims to be a simple e-mail, newsgroup and news feed client

Thunderbird can manage multiple e-mail, newsgroup and RSS accounts and supports multiple identities within accounts. Features like quick search, saved search folders ("virtual folders"), advanced message filtering, message grouping, and labels can help manage and find messages. On Linux-based systems, system mail (movemail) accounts are supported.