Mozilla Thunderbird makes e-mailing safer, faster, and easier with such features as intelligent spam filters, a built-in RSS reader, and quick search. Thunderbird was designed to prevent viruses and to stop junk mail. Thunderbird 3 includes tabbed e-mail, new search tools and indexing, smart folders, support for Firefox's Personas, a simplified setup wizard, and robust junk protections that include phishing and spam filters.
What's new in this version:
GMail supports OAuth2 authentication, removing the need to manually select "allow less secure applications" in Google options for the account. (bug 849540)
Ship Lightning calendar addon with Thunderbird and enable with an opt-out dialog (bug 1113183)
Filter sent messages (bug 11039)
Filter messages when archived (bug 479823)