Release Notes

Thunderbird Desktop

Version 91.0 | Released August 11, 2021

Check out the notes below for this version of Thunderbird. As always, you’re encouraged to tell us what you think, ask for help, or file a bug in Bugzilla.

** Thunderbird version 91.0 is only offered as direct download from thunderbird.net and not as an upgrade from Thunderbird version 78 or earlier.** A future release will provide updates from earlier versions.

System Requirements: Details

  • Windows: Windows 7 or later
  • macOS: macOS 10.12 or later (macOS 11.0 for Silicon)
  • Linux: GTK+ 3.14 or higher

What’s New

new

Native support for macOS devices built with Apple Silicon CPUs

new

Thunderbird now operates in multi-process (e10s) mode by default

new

Latvian language support

new

New user interface for adding attachments

new

Enable redirect of messages

new

Ability to change order of accounts in UI

new

Allow showing empty CC/BCC rows in compose window

new

Warning popup when sending a reply to a likely non-existant email address such as "[email protected]"

new

Warning popup when public recipients of a message exceeds threshold

new

Add support for "X-Unsent: 1" header, to open a saved email in a compose window for editing

new

Add support for non-ASCII characters in recipient addresses

new

Context menu to expand mail list pills in the compose window to the list of recipients

new

Quick Find is now available in the multi-message (thread summary) view

new

Keyboard shortcuts to access To/CC/BCC fields of compose window

new

Allow pinning folder views to the Folder Pane

new

Language packs and dictionaries added to about:support

new

PDF.js viewer now included in Thunderbird

new

OpenPGP: "Copy Key Id" option added to Key Manager context menu

new

OpenPGP: Added config option to disable encrypting saved drafts

new

Encrypt mail to BCC recipients (with warning that it will expose the recipients in the list of keys)

new

CardDAV address book support

new

CardDAV address books automatically detected based on provided user information

new

Access to Outlook Contacts; To enable, set ldap_2.servers.outlook.dirType to 3; This setting may cause startup delays.

new

Suggest replacements for discontinued/incompatible add-ons

new

Chat: Beta-level support for Matrix servers (set chat.prpls.prpl-matrix.disable to false)

new

Calendar: Remote calendar auto-detection now supported

new

Calendar: Calendar and category colors now displayed in selection dropdowns

new

Calendar: "Edit" item added to event context menu

new

Calendar: Support opening of .ics files by double-click

new

Calendar: Thunderbird now informs the operating system that it knows how to open webcal: URLs

new

Calendar: Filter and sort items to be imported in the Import dialog

new

Prompt to choose the identity of an accepted calendar invite when no identity matches the event attendees list

new

Support mid: URL scheme for Related Links in calendar event dialogs

new

Permissions to access calendar and address book are now requested when a GMail account is set up, so that calendar and address book can be accessed without having to re-authorize (see notes)

new

Calendar: Per-calendar and global notification settings (in addition to alerts set in events)

new

Tasks: Undo/Redo support for event and task creation and deletion

What’s Changed

changed

"Master Password" renamed to "Primary Password"

changed

Renamed "Add-ons" to "Add-ons and Themes" and "Options" to "Preferences"

changed

Account setup moved to a tab

changed

Mail recipients that are not found in any address book will no longer appear in red type; invalid addresses will appear red

changed

Clicking on an already-selected pill in the recipient list will now allow editing the address

changed

Folder pane color scheme overhauled with a focus on readability

changed

Sending backend, SMTP protocol, and LDAP protocol implementations rewritten in Javascript

changed

Sending backend, SMTP, and IMAP protocols now operate only in UTF-8 mode

changed

Sending a message will now fail if any recipients are not accepted by the SMTP server

changed

Error messages from an SMTP server are now displayed to the user

changed

UI Customization controls moved to the View menu

changed

End-to-End Encryption "Advanced Settings" are now disabled when encryption is not configured

changed

Movemail support removed

changed

WeTransfer FileLink provider removed

changed

Enterprise policies updated

changed

Printing UI updated

changed

AutoComplete from LDAP directories now searches by substring instead of left-side match

changed

Support dropped for macOS address book integration

changed

Chat modules and custom widgets are now lazy-loaded to improve Thunderbird startup time

changed

Default IRC server for new chat accounts changed to "libera.chat"

changed

Chat: Image based emoticons replaced with Unicode

changed

Calendar: Opening an existing event now opens summary dialog

changed

Calendar: Default to CalDAV when supported by the server

What’s Fixed

fixed

Thunderbird did not properly handle Self-signed certificates on IMAP servers

fixed

Various issues with special and non-ASCII characters in IMAP folders names, especially on Gmail

fixed

Drag & drop operations could be disrupted by incoming mail notifications

fixed

Dragging a folder from an authenticated IMAP server to a not-yet authenticated server fails

fixed

Temporary errors from POP3 servers would cause Thunderbird to stop downloading mail until it was restarted

fixed

Favorite Folder view did not maintain UI state between Thunderbird restarts

fixed

Saved search virtual folders were not retained after restarting Thunderbird

fixed

Thunderbird did not correctly warn about all affected filters when removing a folder

fixed

Manually running filters on a maildir folder did not work

fixed

Partially downloaded messages displayed in a stand-alone window did not refresh after clicking link to download the rest of the message

fixed

An erroneous "Sender" header was displayed in the message preview after viewing certain S/MIME signed emails

fixed

Some temporary files created by the message composer were not automatically removed after closing the compose window

fixed

Archiving messages from an NNTP account made the target folder unusable

fixed

Compose window: The user-configured style for quoted text was not honored

fixed

Message headers in compose window disregarded manual resizing when adding additional recipients

fixed

Various improvements to new message notifications

fixed

A Thunderbird icon pinned to the Windows taskbar reverted to a non-functional placeholder after an update

fixed

Various improvements to recipient pills in message compose window

fixed

Keyboard shortcut to open the Message Security popup did not work on Mac

fixed

Subject column in message lists sometimes showed text from invalid email headers

fixed

Account settings: When creating a new account, some already entered settings did not copy to the Advanced Config dialog

fixed

Default address book preference was not honored in the contacts sidebar

fixed

Import Address Book from CSV did not not allow mapping all available fields

fixed

LDAP address books did not display multi-valued attributes

fixed

Address Book: Users with LDAP admin rights could delete accounts if trying to delete an entry from an address book backed by LDAP

fixed

Some preferences related to an address book were not removed when the address book was deleted

fixed

Shortcut for Advanced Address Book Search (Ctrl+Shift+F) did not work on Linux

fixed

Radio buttons could not be selected on photo tab of an address card

fixed

Windows uninstaller did not always remove all Thunderbird program files

fixed

Chat: Double clicking an account type in new account wizard did not select it

fixed

Chat account settings did not always save as expected

fixed

User nickname colors were not used in chat content

fixed

Chat: Multiple system messages did not collapse

fixed

Calendar: Reminder details appeared editable when viewing an event

fixed

Calendar: HTML rendering in event descriptions restored

fixed

Calendar: The toolbar in the invitation details dialog was not honoring the theme colors

fixed

Calendar: Various dialog updates

fixed

Calendar: Import and export via CSV did not parse years correctly in event dates

fixed

Calendar: Event boxes were not always focused when clicked

fixed

Dragging and dropping an ICS file to the Today Pane did not populate the "New Event" dialog

fixed

Calendar: Reduced flickering effect in Today Pane

fixed

Calendar: The time of day indicator line did not update automatically

fixed

Location field was not preserved when modifying recurring events stored on a remote calendar

fixed

Today was difficult to pick out visually in the month/multiweek calendar views

fixed

Columns in Today Pane were not resizable

fixed

Calendar event text could render outside the confines of the event block

fixed

Event time and event name were not vertically aligned

fixed

Improved formatting of event descriptions with long links, such as Zoom invites

fixed

RSVP replies to invitations sometimes sent from the wrong email address

fixed

Various UI and theme improvements, especially to dark themes

fixed

Various security fixes

Known Issues

unresolved

OTR chat encryption fails on 32-bit Windows builds

Learn What’s Next

Thunderbird keeps getting better. Subscribe to our newsletter and follow us on social media to stay informed.