Mozilla has released Thunderbird version 148 of its widely adopted free and open-source desktop email client, now available for download.
In this update, one of the most visible changes is that the “Favorites” folder can now be selected directly as a destination when using the “Move To” and “File” actions.
On the authentication front, NTLM is now available for Exchange Web Services accounts, plus Yahoo, AT&T, and AOL accounts have been migrated to PKCE.
Several Exchange-related issues were also addressed, including password save failures for new password-based accounts, incorrect manual configuration flows in Account Hub, and endless password prompt loops when empty credentials were submitted.
Moreover, the release resolves a reliability issue where periodic mail checks silently stopped after system sleep or network outages. It also fixes a bug where the donation banner could steal focus while Thunderbird was running in the background.
Folder and message handling received attention as well. Read folders are now removed from the Unread Folders view, untagged messages work correctly again with the quick filter, and unread messages inside collapsed threads are more clearly indicated. The New Folder dialog no longer allows invalid folder creation without a parent folder, and the “Move Message to” filter action is now properly logged.
Google Calendar RSVP logic has been corrected, too, including organizer handling for new events. CalDAV improvements address missing response options for invited calendar aliases and crashes involving multi-attendee invitations. iCal imports no longer misinterpret unknown timezones as GMT, preventing events from being created at incorrect times. Additional fixes address saved searches in unified folders that caused server errors.
Further refinements include corrected status bar localization for folder and IMAP mailbox names, preventing shortcut execution in background mail windows while in Account Hub, and improved handling of unknown OAuth providers during manual EWS configuration. The update also includes general visual and UX improvements.
For more information, see the announcement. Thunderbird 148 is available as a direct download from thunderbird.net.
