Consumers can now downloadfor Windows, Mac OS X and Linux, the foundation said Tuesday. The e-mail application includes a built-in spam filter, an RSS (Really Simple Syndication) reader and improved search and sorting capabilities; users can save the results of a search in a folder and run the search again at a later date, or color-code messages to help sorting.
To ease consumers' migration from other e-mail systems, Thunderbird automatically imports account settings and addresses from Microsoft Outlook, Microsoft Outlook Express, Eudora and Netscape Mail and transports unopened mail from old in-boxes, Mozilla said.
David Hallowell, a Mozilla contributor, said part of Thunderbird's appeal is in its user interface and spam-filtering capabilities.
The e-mail client does not currently include calendar functions, but that feature will be available in a separate application called Sunbird, Hallowell said.
"The main difference between Outlook and Thunderbird is that Thunderbird is simply a mail client and doesn't include scheduling facilities built in--there are currently volunteers working on the Mozilla Sunbird project which will provide calendaring facilities," he said. "This fits in with the Firefox approach of writing applications to do one task well rather than doing a mediocre job by making an application perform various functions that the user may not require."
Sunbird developers have already released a test version of the calendar application, according to the Sunbird Web site.
The Mozilla Foundation has already experienced considerable success with Firefox 1.0, which has been downloaded more than 9 million times and appears to befrom Internet Explorer, according to Web traffic measurement service OneStat.com. But Hallowell said he does not believe the foundation plans to promote Thunderbird in the same way.
"I'm unable to speak officially for the foundation on this matter, but as far as I know there are no plans for a dedicated 'Spread Thunderbird' site. Instead the main aim is to leverage the current Firefox community in promoting Thunderbird," he said. "Firefox and Thunderbird both share the common goal of making the Internet a safer, less annoying and more enjoyable place, so it makes sense to promote Thunderbird as the perfect complement to Firefox."
Gary Barnett, research director at Ovum, said he thinks Thunderbird will do well, but that it will take longer to catch on than Firefox.
"I believe it will be successful, but it will be a slower burn than Firefox," Barnett said. "It will undoubtedly be a harder sell."
One of the problems in persuading people to start using a new e-mail client is that they tend to make more changes to the application settings than they do with their browsers.
"By using a particular browser you don't sell your soul to it in the same way as you sell your soul to your e-mail client," Barnett said. "Once you've set things up, especially if you have calendaring, it's more effort to move. One of the big show stoppers (for alternative e-mail applications) has been users' reluctance to give up Outlook."
Thunderbird 1.0 can be downloaded for free from the Mozilla Web site and is available on CD from Mozilla's online store.
Ingrid Marson of ZDNet UK reported from London.