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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

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 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.
  
• Aboutupport 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?
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