Software Update: Mozilla Thunderbird 78.6.0

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The Mozilla Foundation has released version 78.6 of Thunderbird. Thunderbird is an open source client for email and newsgroups, with features such as support for several mail and news accounts, a spam filter, spell checker, and a customizable appearance. In version 78, a dark mode has been added and other parts of the interface, such as the icons and the screen for composing an email, have also been overhauled. Furthermore, the Lightning calendar add-on is now a standard part of the program, there is a new wizard for the first use and only MailExtensions add-ons are supported. The changelog for this release looks like this:

What’s New

  • MailExtensions: Added


  • Thunderbird now only shows quota exceeded indications on the main window
  • MailExtensions: menus API enabled in messages being composed
  • MailExtensions: Honor allowScriptsToClose argument in windows.create API function
  • MailExtensions: APIs that returned an accountId will reflect the account the message belongs to, not what is stored in message headers


  • Keyboard shortcut for toggling message “read” status not shown in menus
  • OpenPGP: After importing a secret key, Key Manager displayed properties of the wrong key
  • OpenPGP: Inline PGP parsing improvements
  • OpenPGP: Discovering keys online via Key Manager sometimes failed on Linux
  • OpenPGP: Encrypted attachment “Decrypt and Open/Save As” did not work
  • OpenPGP: Importing keys failed on macOS
  • OpenPGP: Verification of clear signed UTF-8 text failed
  • Address book: Some columns incorrectly displayed no data
  • Address book: The address book view did not update after changing the name format in the menu
  • Calendar: Could not import an ICS file into a CalDAV calendar
  • Calendar: Two “Home” calendars were visible on a new profile
  • Calendar: Dark theme was incomplete on Linux
  • Dark theme did not apply to new mail notification popups
  • Folder icon, message list, and contact side bar visual improvements
  • MailExtensions: HTTP refresh in browser content tabs did not work
  • MailExtensions: messageDisplayScripts failed to run in main window
  • Various security fixes

Known Issues

  • Thunderbird performs sluggishly on macOS Big Sur

Version number 78.6.0
Release status Final
Operating systems Windows 7, Linux, macOS, Windows 8, Windows 10
Website Mozilla Foundation
License type Freeware
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