This release has some significant new features, as well as many, many bug fixes.
Full details of all the changes can be found in the Thunderbird 38 release notes.
The good news that we want to share with you today is that Mozilla Thunderbird 38.0 is not only a version number upgrade but it's a feature release that brings some interesting new functionality to the application.
Some of the new features include:
Chat supports Yahoo Messenger
Filtering sent/archived messages
Search multiple address books
Expanded Folder Pane columns
Mail Composition Fixes
Font Handling on Linux
Chat supports Yahoo Messenger.
Thunderbird chat now supports Yahoo Messenger.
Filtering sent/archived messages.
You can now filter on sent and archived messages.
Search multiple address books.
You can now search multiple address books!
Expanded Folder Pane columns.
In the folder pane (the list of folders on the left), you can now show expanded options (Unread, Total and Size) View|Layout|Folder Pane Columns.
Thunderbird 38 now supports the OAuth 2.0 protocol now used by Google for authentication.
Starting in Thunderbird 38, the Lightning calendar add-on is bundled with Thunderbird.
Mail Composition Fixes.
Some idiosyncrasies in the message compose window have been addressed: The composition font is no longer lost after clicking elsewhere in the message and then returning to the end of the line of the text being entered. Also, the composition font is no longer lost after pasting a bitmap from the clipboard. The inline spell checker no longer loses red underlines.
Inline spell checking: New messages will now always be spell-checked in the language selected in Tools|Options|Composition|Spelling|Language and not as before in the last language used. Also, the spell checking language is now always synchronised between subject and message body. You can even compose messages in different languages concurrently now without having to switch dictionaries.
Font Handling on Linux.
Linux provides system fonts "sans-serif", "serif" and "monospace". These font names conflict with the generic CSS font family names. Therefore and for compatibility with Thunderbirds on other platforms, the ability to compose messages using these three fonts was removed on Linux. Users who had selected one of these fonts as their default composition font have to select a different font. Instead of "sans-serif", "serif" or "monospace" users should select "Helvetica, Arial", "Times" or "Courier" (or "Fixed Width") respectively.
The three aforementioned Linux system fonts can still be used as default display fonts.