As expected, Mozilla announced last evening (June 5th) that the thirteen release of both Mozilla Firefox and Thunderbird products are available for download for all supported platforms, including Linux, Mac and Windows.
The Mozilla Thunderbird 13.0 news and email client, used by default on popular Linux distributions, such as Ubuntu 12.04 LTS (Precise Pangolin), brings only one new feature called Filelink, which allows users to send large attachments by sending a link to the file, avoiding bounce back of emails.
Also, if you use Firefox as the default web browser, you should check out Softpedia's announcement for the final release of Mozilla Firefox 13.0.
Linux users can download the Mozilla Thunderbird 13.0 source and binary packages for both 32-bit and 64-bit architectures right now from Softpedia.
Also, don't forget to visit our always up-to-date Thunderbird Extensions section, for the latest add-ons!