Thunderbird 91.3.1: fixes and important changes

Martin Brinkmann
Nov 16, 2021

A new version of the open source email client Thunderbird is now available. Thunderbird 91.3.1 is available for all supported operating systems. Existing installations will be upgraded to the new version eventually, thanks to the built-in automatic updating system. Thunderbird users may check the installed version by selecting Help > About Thunderbird. If the main menu bar is not displayed, try holding down the Alt-key to display it.

The page that opens displays the current version and runs a check for updates. Any update that is found will be installed.

New users can download the latest version from the official Thunderbird website.

Thunderbird 91.3.1

The Thunderbird team lists four changes and a good dozen fixes on the official release notes page.

As far as changes are concerned, there are several that may be important to users of the client.

Thunderbird users, who have add-ons installed, may notice that the email client will run checks for add-on updates automatically after updates now once Thunderbird 91.3.1 is installed on the device.

Extensions that are installed in Thunderbird are configured to check for updates automatically by default. Thunderbird users can disable this in the preferences.

The new update check after the installation of updates is designed to reduce the impact of Thunderbird updates on installed extensions. Sometimes, Thunderbird may introduce changes that may interfere with the running of extensions, unless these are updated.

Another change in the new Thunderbird version is that it now supports the adding of new search engines via URLs. Search engines can be added via Tools > Preferences > General > Default Search Engine.

The FileLink messages template was updated in this release. The team removed the advertisement for Thunderbird.

The last change removes the attachment count of OpenPGP public keys.

The following fixes are mentioned:

  • Mac OS X stability improvements.
  • Thunderbird displayed new mail popups while fullscreen applications were running.
  • Thunderbird did not support messages with the non-standard "koi8r" encoding.
  • Thunderbird opened PDF attachments in Firefox while composing emails.
  • Offline Settings set to "ask me for online state (on startup)" did disable add-ons.
  • A click on links beginning with addons:// in the add-ons manager prompted to pick an application, instead of opening it internally.
  • Address Book drop down of the Contacts sidebar was unreadable on Windows.
  • vCard attachments were not shown when the inline view for attachments was enabled.
  • Imports of ICS files with TODO items failed.

Now You: which version of Thunderbird do you use currently, or do you use another email client?


Thunderbird 91.3.1: fixes and important changes
Article Name
Thunderbird 91.3.1: fixes and important changes
A new version of the open source email client Thunderbird is now available. Thunderbird 91.3.1 is available for all supported operating systems.
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  1. Ryk van Donselaar said on December 8, 2021 at 9:13 pm

    No longer able to access gmail account. Asks for new pw but won’t login.

  2. Dalton Moss said on November 22, 2021 at 8:30 pm

    You know, I get a lot of attachments and I have come to the opinion that that dialog box to open attachments is utterly and ridiculously useless! It is not even consistent between file extensions, offering one now and another one later for the same type–and AFTER you already checked the box! I have heard some technical mumbo-jumbo about mail servers being the focus for the thing but it still seems to do nothing for the regular long term user of Thunderbird.

    1. Wayne said on December 9, 2021 at 11:30 am

      Agree, the attachments issues are super irritating. It’s an are that is still actively being worked on.

  3. Anonymous said on November 20, 2021 at 10:58 am

    dont like the new print preview, no zoom possible. will stay on .v78

  4. owl said on November 19, 2021 at 2:00 pm

    It is also possible to add the extension “uBlock Origin” to Thunderbird.
    Thunderbird: Download uBlock0_1.38.7rc2.thunderbird.xpi, then drag-n-drop it into Thunderbird’s Add-ons Manager pane (Thunderbird 78+ required)

  5. jon said on November 18, 2021 at 6:24 am

    Still getting prompted for default action to take to open a .jpg attachment. Each and every .jpg file. Every single time!!! (and yes, “do this automatically from now on” is checked. It used to work in earlier versions, my first problem started in v91.x. Using iMac.

    I have tried various online suggestions, including deleting .jpeg in preferences->attachments.

    Be nice if we could create custom settings to open attachments in preferences.

    1. Dalton Moss said on November 22, 2021 at 6:32 pm

      I agree. And this is really aggravating. Plus, the new configuration layouts are not an improvement either. I am beginning to wonder about the contributors to this system.

      And the “Sorry to hear that” reply to a thumb down for the “Was this article helpful?” is rather rude, IMO, and shows a certain disdain for the lowly user. If you are going to ask then don’t insult the responder for answering!

  6. Anonymous said on November 17, 2021 at 6:18 pm

    Da oggi pomeriggio non riesco più ad inviare mail. Mi appare sempre “Invio del messaggio non riuscito.
    Non è stato possibile inviare il messaggio perché la connessione al server di posta in uscita (SMTP) è stata interrotta durante la trasmissione. Riprovare.”.
    Thunderbind è selezionato come attendibile da antivirus perciò non è bloccato da quello … anche perchè fino a stamattina funzionava.
    cosa devo fare?

    1. ShintoPlasm said on November 18, 2021 at 9:43 pm

      English please.

      1. anonymous (a different one) said on December 21, 2021 at 12:51 am

        He/she said (translated):

        Since this afternoon I’m no longer able to send mail. I just get “Sending of message failed. It was not possible to send the message because connection to the outgoing mail server (SMTP)[.]com was interrupted during transmission. Retry.”
        Thunderbird is marked as trustworthy by the antivirus, so it’s not blocked by that … also because until this morning it was working.
        What should I do?

  7. Anonymous said on November 17, 2021 at 5:56 am

    I’m at 91.3.0.

    I was hesitant to upgrade from 78.* to 91.*, but after waiting while, I upgraded without any problems. Also by that time the extensions I used were updated to work with 91.*.

    I don’t think I’ve had a problem with any Thunderbird update.

    I’m glad there is a Thunderbird email client.

  8. Ref said on November 17, 2021 at 5:07 am

    Ever since this update, Thunderbird is ALWAYS in dark mode (Even when light theme is selected). Please fix this issue.

  9. Yanta said on November 17, 2021 at 3:00 am

    This program gets worse with every release. All of the add ons that I use are no longer supported.
    One would have thought that digitally signing and encrypting emails in this day and age would be a big deal. Mozilla live in a world where privacy is totally foreign to them.

    being able to selectively use encryption is a must. Not everyone uses encryption so the all or nothing is a joke.

    Mozilla blocked developers from creating add ons with useful functionality. This is typical of Mozilla’s behavior.

    Don’t get me started on the UI – atrocious. I’ve had several attempts at trying to get it to look half decent with very little luck.

    As such, I’m still on v52.9.1. Stable, everything I need works and I have no security issues that I’ve come across. And best of all – all that extra telemetry and data collection they added in later versions is not present in v52.

    1. ShintoPlasm said on November 18, 2021 at 9:43 pm

      T-bird’s UI is the worst of every email app on Windows, on par with some of the monstrosities which exist in the world of Lonux.

  10. Tom said on November 16, 2021 at 11:58 pm

    I’m still running an old version of Thunderbird which works and which supports a decent theme. Much prefer it to Outlook in Office 2019.
    Is it possible to install this latest version to run side by side with an older Thunderbirds version ?
    I fear running install for the new version with overwrite the old and everything will then go very badly wrong !

    1. Iron Heart said on November 17, 2021 at 10:47 am


      You can run Interlink (forked from Thunderbird 52.0, but still updated):

      It can be run alongside a recent version of Thunderbird. Cheers.

      1. Leland said on November 17, 2021 at 10:16 pm

        Can you use your old Thunderbird 52 profile with it or would this cause issues?

      2. Iron Heart said on November 19, 2021 at 7:51 am


        According to this thread, you probably can just transfer the Thunderbird 52 profile without issues:

  11. Phylis said on November 16, 2021 at 6:23 pm

    Still using v. 60.9.1 and love it. Afraid to upgrade and mess things up.

  12. Dave said on November 16, 2021 at 4:21 pm

    Did they ever fix the issue with google calenders?

    (The one where nothing shows unless you hide and then unhide the calender every time you open TB)

    Why does an email client have a search engine?

  13. AgentSmith said on November 16, 2021 at 2:43 pm

    Does anybody know how to REMOVE search engine from Thunderbird?

    I search Internet but cannot find the answer.

    1. owl said on November 19, 2021 at 1:20 pm

      > Does anybody know how to REMOVE search engine from Thunderbird?

      This is possible by editing “extension-preferences.json” in the profile.
      However, it will not work unless it is set to default, so there is no actual harm.
      It is wise not to edit it unnecessarily.

      1. owl said on November 19, 2021 at 1:35 pm

        By the way, “Profile” is
        Thunderbird Menu> Help> More Troubleshooting Information.
        Application Basics
        You can open it by pressing Open Folder in the Profile folder section.

  14. Paul(us) said on November 16, 2021 at 11:01 am

    Thanks Martin, Thunderbird is getting better and better by the release.
    I have read over the new possibility of “the adding of new search engines via URLs.” cant wait to use it.

  15. Juraj said on November 16, 2021 at 10:37 am

    Great, this update broke the dark theme in New message window :(.
    Here we go again,, new bug, steps to reproduce…

    1. Nothin' but Love 4 Mozilla said on November 17, 2021 at 3:52 am

      Not seeing that problem here on a Windows 10 installation. Have you tried disabling add-ons to verify the source of the problem?

  16. Anonymous said on November 16, 2021 at 9:26 am

    Also version 91.3.1 has no security updates

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