Thunderbird 91.3.1

[German]The developers of the Thunderbird email client have released Thunderbird 91.3.1 on November 15, 2021. This is a maintenance and security update for the 91 development branch, which makes minor fixes. Here's a brief overview.


According to the release motes, the update includes the following changes and fixes.


  • OpenPGP public keys will no longer count as an attachment in the message list
  • Adding a search engine via URL now supported
  • FileLink messages' template updated; Thunderbird advertisement removed
  • After an update, Thunderbird will now check installed addons for updates


  • New mail popups were displayed while running full screen applications
  • Messages received with non-standard "koi8r" encoding were not supported
  • Various macOS stability improvements
  • PDF attachments opened in Firefox while composing an email
  • Addons were disabled when "Offline Settings" were set to "Ask me for online state (on startup)"
  • Clicking '"addons://" links in the Addons Manager prompted for an application to open it, rather than opening internally
  • The Contacts sidebar "Address Book" drop down was unreadable on Windows
  • vCard attachments were not shown when using "inline" view for attachments
  • mporting an ICS file with TODO items failed

It looks like no security fixes have been made.

In the blog post Thunderbird 78.x: Upgrade to version 91, and foreseeable problems I had pointed out a signature problem with Outlook. Since nothing is mentioned, the bug should still be present in 91.3.1. Adrian told me in the English blog that he reported the bug in Bugzilla – there it is still "unconfirmed".

At the colleagues of someone writes that he has gone back to version 91.3.0 because the mail client of 91.3.1 does not react anymore when you call the settings. Causes could be language packs, German dictionaries or AddOns.

System requirements

The system requirements for the different operating system versions (see here for more details):


  • Windows: Windows 7  or higher
  • Mac: Mac OS X 10.9  or higher
  • Linux: GTK+ 3.14  or higher

The download of the free Thunderbird is available here. (via)

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