Mozilla releases Thunderbird 142 with several bug fixes and improvements

Mozilla has released Thunderbird 142 nearly a month after 141 came out. This release brings multiple minor changes that users will appreciate.

The first thing you should know is that you can now add a visual signature to your PDF attachments opened directly within the application. The UI got several changes, like the addition of "Copy Message Link" and "Copy News Link" to the header pane's "More actions" menu.

Meanwhile, the older "Copy Message Location" option has been removed from the mail context menu. A new "Reset Folder Order" option has also been added to the folder pane to reset any custom folder sorting you might have done. Folder copy is now enabled within mail server accounts and local folders, a damn useful feature for backups and organization.

Moving on to the bug fixes 142 brings, the issue where right-clicking "List-ID" to unsubscribe has been fixed to prevent a double-encoded

draft subject. Notification sounds now respect your operating system's do-not-disturb mode.

Fastmail calendar support now works correctly again; this bug was caused by missing OAuth settings for the CalDAV protocol when Thunderbird 140 consolidated its authentication code. A reporter on Bugzilla actually diagnosed the problem and provided the exact configuration fix, which Mozilla then implemented. Other bug fixes include:

• Users with attachments open in tabs no longer see an error on restart.
• Non-English Thunderbird no longer creates English special folders on first start.
• Sending from a unified or local folder no longer fails if no default account is set.
• On Linux, the closed caption button is no longer inactive when the mouse is in the screen corner.
• Toggling dark message mode now correctly restores focus and scroll position.
• The message list no longer scrolls back to the top when returning to the mail tab.
• Deleting a single message in a folder using "Group by Sort" no longer fails after selecting all.
• New newsgroups are now added in alphabetical order by default.
• All newsgroup folders are no longer sorted alphabetically after updating.
• Clicking a "mailto:" link to send a signed message no longer fails when Thunderbird is closed.
• Thunderbird now displays contact photos in WebP format from CardDAV servers.
• Installations from the Microsoft Store now open correctly when clicking "mailto:" links.
• The application no longer experiences long load times and UI lag while messages download on initial launch.

In case you missed it, Mozilla is planning to expand Thunderbird into a wider platform, with services like Thundermail to provide email accounts, possibly under the @thundermail.com domain, and Appointment for scheduling meetings with others.

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Posted Wednesday 20 August 2025 at 5:20 am AEST (my time).

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