Thunderbird 91 is available as a manual upgrade

Martin Brinkmann
Aug 13, 2021
Email, Thunderbird

Thunderbird 91, a new major version of the open source cross platform email and communication client, has been released. The new version of Thunderbird is not yet available via the email client's integrated updating functionality.

Users interested in the new version need to download and install it manually; existing installations of Thunderbird will be upgraded in the process to the new version.

Similarly to how Thunderbird 78.x was released, Thunderbird 91 will be offered via the integrated updating functionality eventually.

Thunderbird 91

thunderbird 91

The installation of Thunderbird 91 is straightforward. Download the version from the official Thunderbird website and run the downloaded file afterwards.

Existing installations should be detected automatically and the installation or upgrade should progress without issues.

Thunderbird 91 is a new major version, which introduces new features and changes. The email client is the first to support Apple Silicon CPUs natively, which benefits Mac OS users.

The program makes use of multiple processes by default now, similarly to how Firefox introduced support for the feature a long time ago.

The email account setup process has been improved in the new version of Thunderbird. The email client supports CardDAV address books now, and will detect these automatically based on the email address the user provides. Similarly, remote calendars will be detected automatically to streamline the setup process.

If you set up a Gmail account, Thunderbird will detect the address book and calendar, if available, to suggest to import the data right away.

The team added a new redirect option to the email client. You find it when you select the More button when viewing an email, or when right-clicking on emails, as it is listed in the context menu.

mail redirect thunderbird

Mail redirects work similarly to mail forwarding, but with several differences. Redirected emails retain the original email body and subject, whereas forwarded ones are changed somewhat.

Another useful feature of Thunderbird 91 is the ability to change the order of accounts in the user interface; this can't be done in the main window. You need to open Tools > Account Settings, and use drag & drop to sort accounts.

Smaller features of Thunderbird 91

  • Support for Latvian language.
  • Attachments are no longer listed in the header area, but at the bottom of the email window.
  • Compose window may show empty CC and BCC rows.
  • Warning popups when
    • an email address may not exist.
    • public recipients exceed thresholds.
  • Support for non-ASCII characters in recipient addresses.
  • Support for X-Unsent: 1 header to open saved emails in compose windows for editing.
  • Context menu to expand mail list pills in the compose window to the list of recipients.
  • Quick Find is available in the multi-message view.
  • New keyboard shortcuts to access To, CC and BCC fields in the compose window (use Ctrl-Shift plus T, C or B to jump to the fields).
  • Folder views can be pinned to the Folder Pane.
  • About:support displays installed language packs and dictionaries.
  • PDF.js viewer integrated in Thunderbird to view PDF documents in the email client.
  • OpenPGP changes
    • Option to disable encrypting saved drafts.
    • Copy Key ID added to context menu of Key Manager.
  • Encrypt mail to BCC recipients.
  • Support for Outlook contacts. Need to set ldap_2.servers.outlook.dirType to 3 in the advanced configuration.
  • Support for Matrix servers (Beta, set chat.prpls.prpl-matrix.disable to FALSE to enable in advanced config).
  • Suggestions for incompatible/discontinued add-ons.
  • Calendar:
    • Colors now displayed in selection dropdown.
    • New Edit context menu item.
    • Double-click to open ICS files.
    • Thunderbird is a file handler for webcal URLs.
    • Filter and sort items are imported in the import dialog.
    • Prompts when no identity matches the attendees list of an event invitation.
    •  mid: URL scheme supported for Related Links.
    • Per-Calendar and global notification settings.
  • Undo and redo support for event and task creations/deletions.

The list of changes is equally long. Names of some features were changed: the master password is now called primary password, add-ons was renamed to add-ons and themes, and options is now called preferences.

Account setup happens in a dedicated tab now, and red indicates invalid email addresses in compose windows exclusively now (opposed to highlighting all emails not found in the address book).

Thunderbird may start more quickly as chat and custom widgets are lazy-loaded.

Here are the other changes:

  • A click on a selected email address in the compose window allows you to edit it.
  • Folder pane color scheme changed, focusing on readability.
  • SMTP protocol, LDAP protocol and sending backend implementations rewritten in JavaScript.
  • Message sending will fail if any of the recipients are not accepted by the SMTP server.
  • SMTP server errors are shown now.
  • UI customization options moved to View menu.
  • Movemail and WeTransfer FileLink support removed.
  • Enterprise policies updated.
  • Printing UI updated.
  • Image-based emoticons replaced with Unicode.
  • Summary dialog displayed when opening existing events.
  • CalDAV is the default if supported by the server.

The developers have fixed a significant number of issues besides all that. You find them listed on the official release notes page.

The developers list one issue: OTC chat encryption fails on 32-bit Windows builds.

Now You: what is your take on the new Thunderbird 91?

Thunderbird 91 is available as a manual upgrade
Article Name
Thunderbird 91 is available as a manual upgrade
Thunderbird 91, a new major version of the open source cross platform email and communication client, has been released.
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  1. JMGG said on January 19, 2012 at 8:25 am

    You said that Outlook isn’t your main email client, so which is your main one?

    1. BalaC said on January 19, 2012 at 9:42 am

      I think its thunderbird

    2. Martin Brinkmann said on January 19, 2012 at 10:15 am

      It is Mozilla Thunderbird.

  2. Salaam said on September 24, 2012 at 9:52 pm

    Awesome! This actually solved my problem… what a stupid bug.

  3. Claud said on December 19, 2012 at 2:08 am

    If this is the same bug that I’ve encountered, there may be another fix: (1) hover over open Outlook item in Taskbar, cursor up to hover over Outlook window item, and right-click; (2) this should give you Restore / Move / Size / Minimize / Maximize — choose Move or Size; (3) use your cursor keys, going arbitrarily N/S/E/W, to try to move or size the Outlook window back into view. Basically, the app behaves as though it were open in a 0x0 window, or at a location that’s offscreen, and this will frequently work to resize and/or move the window. Don’t forget to close while resized/moved, so that Outlook remembers the size/position for next time.

    1. Lynda said on February 12, 2013 at 3:37 pm

      THANK YOU Claude!!! I could get the main window to launch but could not get any other message window to show on the desktop. You are my hero!!!!

    2. Chad said on November 20, 2018 at 4:24 pm

      Solved my issue! 6 years later and this is still problem…

    3. Ivan X said on January 21, 2021 at 4:50 pm

      Fantastic. Thank you. Size did the trick.

  4. Andrew said on October 26, 2013 at 7:06 am

    This solved my Outlook problem, too. Thank you. :)

  5. Charles said on December 7, 2013 at 7:23 pm

    Thank you so much, this started happening to me today and was causing big problems. You are a life saver, I hope I can help you in some way some day.

  6. garth said on November 7, 2014 at 7:13 pm

    You are a god – thank you!

  7. Faisal said on February 9, 2015 at 10:09 am

    thanks a lot…. work like charm.. :-)

  8. Simon said on March 24, 2015 at 11:36 pm

    Yah…thanks Claude. I’ve been having the same problem and tried all the suggestions…your solution was the answer. It had resized itself to a 0/0 box. Cheers

  9. Olu said on April 14, 2015 at 1:35 pm

    Excellent post. This had me baffled even trying to accurately describe the problem. This fixed it for me.
    Thank you

  10. Coenig said on July 23, 2015 at 7:36 am

    Thanks a lot for the article. Don’t know why it happenend, don’t know how it got fixed, but it was really annoying and now it works :-)

  11. Fali said on January 20, 2016 at 4:19 pm

    Thanks a lot. I was facing this issue from past 3 week. I tried everything but no resolution. The issue was happening intermittently and mainly when I was changing the display of screen ( as i use 2 monitors). The only option i had was to do system restore. But thanks to you.

    1. MIki said on January 10, 2019 at 11:54 am

      I’ve been tried to sole this problem for 12hours. Your comment about changing the display of screen helped me a lot!! Thanks!!

  12. Christina said on January 20, 2016 at 6:14 pm

    Thank you…don’t know why this happened but your instructions helped me fix it. Running Windows 10 and office pro 2007

  13. Oz said on July 22, 2016 at 3:20 pm

    Great tip! Thanks!

  14. Tracy said on September 1, 2016 at 4:48 pm

    Worked for me, too – thank you!!!

  15. shawn said on September 9, 2016 at 10:25 am

    It’s Worked for me, too
    thank you very much!

  16. Jari said on October 31, 2016 at 11:53 am

    I had a similar issue with Outlook 2013 on Windows 10 and this helped me to fix it. Thank you very much!

  17. Michel H said on November 30, 2016 at 11:08 pm

    Thank you so much. Solved!
    Considering you published this in 2012, incredible not been debugged by Microsoft.
    Thank you again. M

  18. Ziad Bitar said on January 9, 2017 at 2:00 am

    This problem was faced by only one user logging to TS 2008 r2 using outlook 2010.The issue was resolved.


  19. Anonymous said on February 15, 2017 at 5:24 pm

    Great tip. Thank you!!!! If it helps, I had to use the Control Key and the arrow keys at the same time to bring my window back into view. Worked like a charm.

  20. Rochelle said on March 6, 2017 at 11:59 am

    Thank you, this worked !!!!

  21. anom1234 said on May 20, 2018 at 11:20 pm

    Man, you are a fucking god. Thanks a lot, what an annoying bug!!

  22. JC said on October 12, 2020 at 2:14 pm

    Awesome, this post solved the issue. Many thanks!

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