Thunderbird 3 is coming out soon, and it's accessible!

The release of Thunderbird 3 is just around the corner. Aside from all the great new features Thunderbird 3 has in general, its accessibility story is also one which should be celebrated once the release has happened.

Thunderbird 3 is based on the Gecko 1.9.1 platform, which is the same version that Firefox 3.5 is based on. As such, Thunderbird 3 has learned all the great new features of the platform, many of which have a significant impact on users with disabilities. Please allow me to highlight the major improvements and new features.

Support for new accessibility APIs

Thunderbird 3 supports the IAccessible2 standard on Windows. IAccessible2 is a major enhancement to Microsoft Active Accessibility (MSAA), which allows assistive technologies to directly interact with the rich content an HTML e-mail message can have, through a defined set of APIs. Screen readers for the blind, for example, no longer need to rely on old-school screen-scraping methods to try and guess what the application is showing. Instead, headings, block quotes (such as in quoted messages) etc. are all identifiable without question. Font and styling information is available as well. NVDA 2009.1, Window-Eyes 7.1 and JAWS 10 and above take advantage of these technologies already and offer a hugely improved experience for their user bases over what Thunderbird 2.0 had to offer.

This also includes support for in-line spell checking. If enabled, screen readers can identify misspelled words just like in Firefox, and users can go and correct their mistakes on the fly without having to invoke the extra spell checking dialog.

Accessibility on the GNOME Desktop

Thunderbird 3 is accessible to Orca users on the GNOME desktop in Linux. While Thunderbird 2 offered close to no accessibility support, Thunderbird 3 offers a wide range of accessibility to visually impaired users.

Also, the support for ATK/AT-SPI allows other assistive technologies such as GOK (GNOME On-screen Keyboard) to interface with Thunderbird and allow the use by people with motor impairments.

Tabbable and properly labelled message headers

When reading messages, most of the header fields of a message are now reachable via the tab key. This is a huge improvement for any keyboard user. Access includes the “star” that allows to quickly add a contact to the address book or to edit a previously added contact.

All these fields and controls also have proper accessibility labels so that screen reader users immediately know what they’re interacting with.

One known problem is that the multi-functional “reply” control currently isn’t part of the tab order.

Better support when composing messages

Aside from the above mentioned API improvements, the UI also received some love to better communicate the happenings when filling out the from:, to: etc. fields while composing a message. Selecting a different field type now also does not throw newer versions of screen readers into limbo or confused states any longer. Working with the Contacts side bar is also supported.

Over-all UI improvements

Over-all, the various dialogs in Thunderbird such as Tools/Options, Tools/Account Settings and others have received a major accessibility overhaul esp with regards to properly labeling textboxes, radio groups and other XUL widgets so screen reader users get accurate information while tabbing through. Infact, a Thunderbird XUL UI fix was my very first patch when I started contributing to Mozilla. 🙂

New UI features were also made accessible

New UI features such as the all-new facetted search were also made largely accessible. The new Search, for example, makes heavy use of WAI-ARIA to allow both an appearance that’s visually appealing and keyboard and assistive technology communication that’s accessible. The one exception in this new piece of the product is the graph that shows the search results over time. This is based on SVG, which is totally inaccessible at the moment.

A call-out to Thunderbird extension developers

With the above improvements now being in place, it is equally important for Thunderbird extension developers to follow these simple rules to make their extensions accessible, as it is for developers of extensions for Firefox. DOM Inspector offers an accessibility view which allows you to check whether your XUL has proper labels for textboxes and other good markup! Also, don’t be shy to ask questions! The accessibility team hangs out on the #accessibility channel on and will be happy to assist!

A few known problems remain

As always, nothing can be perfect, but we’re striving to be as perfect as possible. Having said that, there are a few issues that remain, but for which fixes are already visible on the horizon:

  • When viewing messages as threads, the fact whether a thread is expanded or collapsed is not yet communicated to screen readers. This will be different once a new version of Thunderbird switches to using Gecko 1.9.2 or later, which includes the all-new tables support.
  • The same is true for the “subscribe” dialog for newsgroups and IMAP folders. Right now, screen readers do not yet get the state whether a certain folder is checked or not. This will also change with a switch to the new Gecko platform.
  • Folders in the folder pane cannot be navigated to using first-letter navigation. I’m hoping we’ll find a solution to this often voiced request in the future.
  • The picker for rearranging the columns in the message list isn’t accessible via the keyboard yet. You can use the mouse emulation of your screen reader to get to that button to the right of the column headers to access options.


I’d like to thank everyone who has been writing to me over the past two years pointing out Thunderbird accessibility issues. As was expected, these actually made up a higher volume than Firefox since there were more UI-related issues. Keep the feedback coming!

I’d also like to extend a huge thank you to the team at Mozilla Messaging and the voluntary contributors who all helped with implementations, reviews, suggestions and advice while improvements for Thunderbird 3 were requested, triaged and acted upon. I really feel that accessibility is being taken seriously, and I honestly hope that a lot of users worldwide will show their appreciation by downloading and using Thunderbird 3 when it comes out! I’ve been using it for over 2 years now while it was being developed and haven’t regretted making the switch!

Keep up the good work!

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