This article describes the major changes in Thunderbird version 5. For a complete list of bugs that have been resolved in the release, refer to the list maintained on The Rumbling Edge blog or the Thunderbird Builds thread on MozillaZine. For information relevant to developers, see "Thunderbird 5 for developers" on the Mozilla Developer Network.
Note that this list was compiled as of the beta 1 build of Thunderbird version 5 and is subject to change.
Thanks to the folks at MozillaZine whose Thunderbird 5.0 - New Features and Changes article was one of the information resources used for this page..
In outgoing messages, if you attach a file to a message, the size of the file is displayed in the attachment window. (This helps you avoid sending overly large files as attachments.)
When you receive a message that has an attachment, the attachment pane (located beneath the message pane) has new information and options.
The number of attachments and the sum of attachment sizes is displayed, as well as a button with various options. If there is only one attachment, the attachment's file name is also displayed. If there are multiple attachments, click the arrow button to the left of the attachment summary to see details for each file.
The button has the following options (with "save" / "save all" as the default):
You can access the same functionality by selecting File | Attachment from the drop-down menu.
See Archived Messages for general information about archiving.
You can configure how archived messages are organized via the Copies & Folders page in the Account Settings dialog (ToolsEdit | Account Settings | <account name>):
As you change configuration options, the panel at the bottom of the dialog will show you how your archive will look.
You can disable archiving for one or more accounts. This will also disable the keyboard shortcut, the button on the message header and the Message | Archive menu option.
To disable archiving:
1. Open the Account Settings dialog and select the desired account from the panel on the left (ToolsEdit | Account Settings | <account name>)
2. Select Copies & Folders and uncheck "Keep message archives in".
There is a new option on the Help menu that displays information about your system, account configuration, etc. This can be used to troubleshoot Thunderbird problems. For example, if you are logging a support question on the Thunderbird Support Site, you can include the information provided by this page with your support request.
You can also generate an email that includes the information on the page. Your personal information (such as your email address, account name and password and messages) is not displayed on the troubleshooting page or included in an email generated from that page. However the server names that you connect to are included on the page and in the report.
When adding recipients to messages, by default only one address field is enabled. After entering the desired address (or using the address book to select an address), click Enter or Tab to activate another address field. Click on the button to the left of the address field to select the type of recipient ("To", "CC", etc).
Thunderbird now uses the display name from the address book in both the message list and the message pane (assuming that the address book preference and the Reading and Display preference are both set to prefer the display name). In previous versions, only the message display was using the display name from the address book. For more information see Display name in message list and message pane.
You can now click and drag tabs into different positions. (The tab on the far left cannot be repositioned.)
There are new tab options that support the new tab re-ordering functionality.
The New Account Wizard has been streamlined and improved. See Automatic Account Configuration for details.
It is now possible to import a contact file in the popular vCard file format.
From the Tools | Import... menu, select Address Books and then vCard file ( *.vcf).
If you disable Thunderbird's automatic update checks (via Thunderbird | PreferencesTools | OptionsEdit | Preferences | Advanced | Update) you can manually check for updates by selecting Thunderbird | About ThunderbirdAbout | About ThunderbirdAbout | About Thunderbird. The Check for updates menu item has been removed from the Help menu.
In previous Windows versions, the Thunderbird installer created a shortcut on the Windows menu for opening Thunderbird in safe mode. This has been removed.
If you are having problems with Thunderbird, try starting Thunderbird with add-ons disabled (Help | Restart with Add-ons Disabled).
When changing folders, Thunderbird now displays the contents of the IMAP folder immediately (based on the cache) and then downloads new headers and updates based on sync flag changes. This makes the folder contents display more quickly. For more information, see "Faster switching to IMAP folders in Thunderbird trunk nightly builds" on Bienvenu's blog.
By default, Thunderbird will now compact folders when compacting will save over 20 MB in disk space. These settings can be modified on the Thunderbird | PreferencesTools | OptionsEdit | Preferences | Advanced | Network & Disk Space menu.
Thunderbird and Firefox are based on the same underlying layout engine (code-named "Gecko"). In the past, people have found it confusing that the version numbers for Firefox, Thunderbird and Gecko are all different. (In fact, we have even had to maintain charts on the Mozilla websites that show which versions of Firefox and Thunderbird map to which versions of Gecko.) Therefore, the Thunderbird group has decided to follow the initiative of the Firefox group and use the same version number as Gecko (currently "5").
In a related initiative, Firefox and Thunderbird are adopting "schedule driven" release processes, which means that we will have more frequent releases based on a fixed schedule. This will make it easier for us to provide fast security fixes, and will also allow us to ship enhancements more quickly as the process will force us to be more modular in our development approach.
Frequent releases means that Thunderbird version numbers will increment quickly. In fact, we will probably be in the double-digits by the end of this year. However, we intend to de-emphasize the version numbers (which have always been somewhat arbitrary) in our communication and simply stress that people should keep their versions up-to-date.