Thunderbird Updates & Release Notes

What’s New

• Linux tray icons indicate unread mail and show its count in the tooltip
• Graph calendars are auto-detected on new account creation

Fixed

• Non-ASCII IMAP tags could exceed server length limits and be rejected
• Zoom Text Only option did not work in the View menu
• Multiple messages were printed even after canceling the print dialog
• Save All and Detach All failed for attachments with invalid filename paths
• First Wrap Long Lines toggle did nothing in View Source
• POP3 NTLM authentication failed because the password was sent incorrectly
• Search Messages menu option was enabled but did not work for saved search folders
• Quick Find shortcut (/) only worked after Ctrl+F was used once
• Unicode email addresses could hide different Reply-To destinations
• Newsgroups with UTF-8 names could display duplicate or incorrect messages
• View > Folders did nothing in Calendar and Tasks tabs
• Global search results did not display recipients in the To field
• Forwarding malformed MIME messages could omit attachments
• Retry and Save Locally failed after a sent-folder copy error
• Closing an unmodified compose window prompted to save when using Body Text
• MP4 attachments could be truncated when forwarding messages
• Inline images disappeared when editing local or POP messages as new
• EWS/Graph accounts could fail when outgoing server settings were incomplete
• Account Hub Edit Configuration did nothing for Exchange and Graph accounts
• First message filter condition could not be removed even when others existed
• CardDAV address book sync stopped when the server rejected an invalid sync token
• CardDAV passwords were not saved, causing repeated login prompts after restart
• Thunderbird could hang on startup when restoring IMAP message and PDF tabs
• Malformed message database files could cause excessive CPU usage
• IMAP namespace root folders were inaccessible due to duplicated folder names
• Excessive Microsoft Graph requests caused throttling and delayed message display
• SMTP addresses with line breaks could inject unintended commands
• POP3 sessions remained active after canceling the password prompt
• Remote content could load in news articles with missing message headers
• RSS feeds could inject arbitrary Message-ID and References headers
• Large ICS calendar files could exhaust memory and freeze Thunderbird
• CalDAV calendars could stop syncing after a network error until restart
• Account Hub failed to discover CalDAV calendars for OAuth2 accounts
• Yearly recurring events with multiple times per day only appeared at the first time

Visual and UX improvements

Security fixes

As always, you’re encouraged to tell us what you think, ask for help, or file a bug in Bugzilla

Fixed

• Attach File dialog failed to open when the previously used folder was unavailable
• Troubleshooting falsely reported crash reports were not configured when available
• Switching to Unified Folders could leave All Folders enabled and not change view
• Archived Inbox folders ignored localized names and appeared as "INBOX"
• Plain-text inline forwards omitted signatures placed below the quote

Security fixes

As always, you’re encouraged to tell us what you think, ask for help, or file a bug in Bugzilla

Changed

• Quick filter responsiveness has been improved
• ExtensionSettings policy installs add-ons from update_url when install_url not set

Fixed

• Copy Link Location only copied detached attachment filenames instead of full paths
• Thunderbird could crash while performing a Body search
• Troubleshooting falsely reported crash reports were not configured when available
• Right-clicking inline images zoomed them instead of opening the context menu
• Switching to Unified Folders could leave All Folders enabled and not change view
• Archived Inbox folders ignored localized names and appeared as "INBOX"
• OpenPGP key management had unlocking, handle leak, and protection state issues
• OpenPGP backup password text could not be copied and context menu was transparent
• Quick Filter failed to match accented names when searching without accents
• Holding Ctrl+Enter could unintentionally confirm the send prompt and send duplicates
• Plain-text inline forwards omitted signatures placed below the quote
• Remote content exceptions without a scheme only applied to HTTP, not HTTPS
• Remote content exceptions incorrectly allowed wildcard hostnames like *.example.com
• Saved CalDAV/CardDAV credentials could be forgotten after restarting Thunderbird
• CardDAV setup failed without prompting for a password
• CardDAV address book sync failed to fetch newly added contacts
• CardDAV updates could corrupt vCard REV timestamps
• CardDAV discovery could fail on valid multi-status responses with mixed status codes
• SMTP Kerberos authentication failed on Linux with STARTTLS
• POP accounts repeatedly showed connection errors when Thunderbird started offline
• Matrix SSO with Save Token disabled reopened the login flow indefinitely
• RSS filtering could lose tags and stall processing of later feed items
• CalDAV password prompts did not identify the username or calendar
• Calendar event edits could fail with localization error in the event dialog
• Updated calendar credentials were not saved from the authentication prompt

Visual and UX improvements

Security fixes

As always, you’re encouraged to tell us what you think, ask for help, or file a bug in Bugzilla

Changed

RNP command-line utilities are no longer included with Thunderbird

Thundermail built-in add-on updated to v2.0.16

Fixed

Ctrl+Shift+K could fail to open the Quick Filter UI

Nested S/MIME signed parts could fail to render

Thunderbird could hang when waiting for IMAP server greeting during account setup

Gmail OAuth2 authentication could intermittently fail on Windows

AppUpdatePin policy did not prevent Thunderbird from updating beyond pinned version

"What's New?" linked to Release channel notes instead of ESR release notes

Security fixes

As always, you’re encouraged to tell us what you think, ask for help, or file a bug in Bugzilla

What’s New

• Enterprise policy DisableChat disables Thunderbird Chat functionality
• Enterprise policy DisableFileLink disables Thunderbird FileLink functionality

Changed

• Preference mailnews.headers.minNumHeaders has been removed
• Allow viewing remote content in OpenPGP messages encrypted with integrity protection
• RNP command-line utilities are no longer included with Thunderbird
• IMAP/POP manual config port field is now optional
• Thundermail built-in add-on updated to v2.0.16

Fixed

• Ctrl+Shift+K could fail to open the Quick Filter UI
• Message list could show the wrong sender for messages
• Status bar could remain active and cause 100% CPU usage after activity ended
• OpenPGP discovery failed to find replacement keys after a key was revoked
• Valid RSA OpenPGP keys could be rejected, preventing encryption
• Sent messages could silently fail to save to the IMAP Sent folder
• Sending message did not fail gracefully with malformed references header
• Thunderbird could hang when waiting for IMAP server greeting during account setup
• Account Hub account creation could fail with malformed URI
• Custom OAuth Endpoint Host incorrectly required a full URL instead of a domain
• Message filters could falsely match when evaluating search term failures
• CardDAV address books could fail to sync when no password prompt was needed
• Yahoo emails appeared blank with MIME handlers disabled via mailnews.display.disallow_mime_handlers
• Pending moves within the same IMAP account could make messages disappear
• Inline images could disappear after editing and resaving drafts
• SMTP OAuth2 failed when large access token exceeded command line length limit
• Gmail OAuth2 authentication could intermittently fail on Windows
• Exchange NTLM authentication failed when updated passwords were not saved
• SMTP AUTH LOGIN could fail after username challenges and close the connection
• AppUpdatePin policy did not prevent Thunderbird from updating beyond pinned version
• Recurring events could appear after their configured end date
• CalDAV task body could remain outdated after syncing changes from another client
• CalDAV invitations could fail when accepted before the calendar synced

Visual and UX improvements

Security fixes

As always, you’re encouraged to tell us what you think, ask for help, or file a bug in Bugzilla

Fixed

Detached attachment links were truncated when folder path contained &
Save All, Detach All, and Delete All failed after deleting one attachment
Blank 1970-dated messages could appear from incomplete message file copies
Forwarded messages could display incorrect encoding
Manual Get Messages failed after startup until toggling offline mode
Thunderbird could crash on shutdown while waiting for OAuth2 password entry

Security fixes

As always, you’re encouraged to tell us what you think, ask for help, or file a bug in Bugzilla

What’s New

• OpenPGP key properties can print debug information to the Error Console
• External browser login flow enabled for Yandex
• Custom OAuth support for issuer ID and client secret field for IMAP and POP3
• Custom OAuth support for POP3
• Enterprise policy DisableUpdateSettings prevents users from changing update settings
• Enterprise policy DisableDataCollectionSettings prevents users from changing data collection setting
• Enterprise policy DisableMessageForwardingFilters prevents message filters from automatically forwarding messages

Changed

• Preference mail.offer_experimental_features renamed to mail.experimental_features_settings.enabled
• Thundermail built-in add-on updated to v2.0.11

Fixed

• Detached attachment links were truncated when folder path contained &
• Opening a PDF attachment in a tab displayed empty tab
• POP3 folders with names over 55 characters could become duplicated after upgrading
• Folders with invalid filename characters could show hashed names if cache was lost
• Save All, Detach All, and Delete All failed after deleting one attachment
• Renaming folders could reset folder settings
• Subscribing an IMAP folder and subfolder together failed to subscribe the subfolder
• Some newly fetched POP messages were not marked with new star after startup
• Sorting after deleting the only child message removed the parent from view
• OpenPGP signing failed with external GnuPG when the primary key could not sign
• Remote content could load in encrypted messages opened from files
• Sent message with expired S/MIME certificate wrongly showed untrusted CA warning
• PDF attachments from compose windows could wrongly be detected as HTML
• Saving unconfirmed recipients could create invalid address pills with >>
• External browser OAuth failed when a browser preconnection closed first
• Users could not set up custom OAuth for Exchange accounts
• Pressing Enter on Windows system tray icon did not restore Thunderbird window
• Inline attachments incorrectly changed the message channel content type
• Message loading was slow while discovering large numbers of IMAP folders
• SMTP authentication failed when usernames contained non-ASCII characters
• Unsupported EWS archive folder prevented all mailbox folders from syncing
• Manual Get Messages failed after startup until toggling offline mode
• Case differences in CalDAV email addresses caused duplicate invitations
• Accepted CalDAV invitations could be saved to the wrong calendar

Visual and UX improvements

Security fixes

As always, you’re encouraged to tell us what you think, ask for help, or file a bug in Bugzilla

What’s New

S/MIME popup shows signature, digest, encryption algorithms and key sizes

Default address book for manually added contacts configurable with mail.addr_book.add_item_default_uri

Enterprise policy DisableQRExport can disable QR export

OAuth add-ons can override built-in settings for selected domains and hostnames

Manual account config streamlined with Exchange, Graph, and custom OAuth support

Custom OAuth support for IMAP and SMTP servers

PKCE and external browser fields added to custom OAuth settings

Enterprise policy DisableExperimentalFeatures for disabling experimental features

Fixed

Unread count dock badge disappeared on macOS restart when no mail window opened

IMAP tags did not sync automatically across clients

Embedded SVG images appeared broken when Display Attachments Inline was disabled

Holding arrow keys failed to smoothly navigate the folder pane

Mark and Tag menu bar items were disabled in search results

Quick Filter ignored address book display names shown in message lists and headers

Attachment filters could disappear or return no results in global search

Body search failed for quoted-printable messages ending on a soft line break

Failed encrypted send did not preserve draft

Failed account setup left an incoming server that blocked account recreation

Removing an account did not remove its OAuth token from the password manager

Account Hub prompted for calendar credentials immediately after successful login

Filters could copy empty messages to Local Folders during startup mail download

Closing message filters wrongly warned completed newsgroup filters were running

Autoscroll icon was missing directional arrows in scrollable messages

Apple Mail text attachments may not appear in MIME messages

Forwarded messages could display incorrect encoding

Thunderbird could crash due to improper database memory handling

Thunderbird could crash on shutdown while waiting for OAuth2 password entry

Thunderbird could crash while loading mail folders

Custom OAuth could not be disabled

Legacy IMAP tag changes were not sent to the server and reverted after refresh

Deleting an Exchange account retained the outgoing server settings

CalDAV calendars with offline support could stop fully synchronizing events

Offline cached ICS calendar changes were silently lost after reconnecting

Thunderbird upgrade disabled composition toolbar

Thunderbird upgrade disabled Settings menu for versions before macOS 13

Windows jump list menu no longer functioned correctly

Visual and UX improvements

Security fixes

As always, you’re encouraged to tell us what you think, ask for help, or file a bug in Bugzilla