The first Beta version of email client Thunderbird 3.0 has been made available.

The release is the first from Mozilla Messaging, a spin off organisation that took over the email client after Mozilla decided it didn't want to continue working on the application in 2007.

The new version of Thunderbird features a tab-based interface, similar to Firefox's, and a new add-on manager, as well as improvements to the address book and the message reader view. Beta 1 also adds integration with both Windows Vista 's built-in search feature and the Address Book within Mac OS X.

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"In some ways, this is a typical beta. We've changed a lot of code since Thunderbird 2, and we need a lot of people to tell us if we've made any boo-boos when fixing bugs. [But] in some other ways it's far from a typical beta. In particular, unlike the traditional definition of a beta release, we're definitely not done making feature changes, including some pretty significant feature work that we expect will be integrated in Thunderbird 3 in later beta releases," said David Ascher, CEO of Mozilla Messaging, in a blog post.

Conversation, which will let users view emails they sent at the same time as the replies received - a function found in Gmail, is one of the features that will be available in the future.

"This lets you view the messages you sent interspersed with the messages you received, but also messages from earlier in the conversation which you may have archived," Ascher explained.

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"As always, we love to get ideas for interesting new capabilities we can bring to the platform," Ascher added.

"We're focusing on some of the basic capabilities we think are crucial to solving today's mail problems, such as search and message management, but it's a huge field and e-mail users are desperate for innovative ideas."

Compatible with Windows, Mac OS X and Linux, Thunderbird 3.0 can be downloaded from Mozilla's site.

See also: Mozilla patches Thunderbird 2 holes