Mozilla released thunderbird 3.1 Release Candidate 1. It is having many new features and improved Stability, Memory, and Password Handling than the older version. The new features are
1. Faster Search Results
2. Quick Filter Toolbar- this will allow you to filter the messages easily.
New Quick Filter Toolbar lets you filter against search terms, tags, starred messages, address book contacts, new emails, and attachments.
3. New Migration Assistant
4. Saved Files Manager
5. Mail Account Setup Wizard
Read more about the Mozilla Thunderbird 3.1 Release Candidate 1 here
While this release is considered to be stable, it is intended for developers and members of our testing community to use for early evaluation and feedback. Users of this latest released version of Thunderbird should not expect all of their add-ons to work properly with this milestone.