Mozilla Thunderbird 3 is a free Web mail handler, a strong desktop client with superior speed and responsiveness time. It is a MS Outlook replacement, very powerful for managing archives and Web mail offline, which loads fast, even when filled by multiple folders and RSS feeds.
The basic features remain: junk mail filters, HTML support, multiple accounts, POP, IMAP, and Microsoft Exchange server support. Security features include S/MIME, digital signing, message encryption, and a built-in phishing detector.
New features include a new activity manager, a new Gmail-like e-mail archive functions, improved Growl notifications, and more keyboard shortcuts. The search tool integrates results with Spotlight desktop searches, along with Growl notifications and integration with the OS X address book.
Another improvement is the tabbed user interface: double-clicking a message opens it in a new tab. Plus Thunderbird will re-open the same tabs that were previously opened when closing and then restarting the program.