Mozilla Thunderbird is a free, open source, cross-platform email, news and chat client developed by the Mozilla Foundation. The project strategy is modeled after Mozilla Firefox, a project aimed at creating a web browser. On December 7, 2004, version 1.0 was released, and received over 500,000 downloads in its first three days of release, and 1,000,000 in 10 days. Thunderbird is an email, newsgroup, news feed and chat (XMPP, IRC, Twitter) client. The vanilla version is not a personal information manager, although the Mozilla Lightning extension adds PIM functionality. Additional features, if needed, are often available via other extensions. Thunderbird can manage multiple email, newsgroup and news feed accounts and supports multiple identities within accounts. Features like quick search, saved search folders ('virtual folders'), advanced message filtering, message grouping, and labels help manage and find messages.
Contributions by Minghong, Gries818, and ShaunMacPherson.