Mozilla has released Thunderbird 1.5, the latest version of its e-mail client. The company said that it offered several new features, including better security, automatic updating and other enhancements aimed at providing a more user-friendly e-mail experience.

The software is available as a free download.

According to Scott MacGregor, technical lead on Thunderbird for Mozilla, there have been 18 million downloads so far of the software, which appeals to both consumer and business users. He said that while most think of Thunderbird as a good alternative for a consumer application such as Microsoft's Outlook Express, it also is comparable to enterprise e-mail software such as IBM's Lotus Notes and Microsoft's Outlook.

MacGregor said some large corporations have migrated to Thunderbird for their corporate e-mail, several of those deployments having more than 40,000 users on the system. However, he said he is not at liberty to provide the names of those companies.

Among the new security features in Thunderbird 1.5 are Kerberos authentication and integration with server-side spam filtering. The new client also includes a built-in phishing detector to help protect users against e-mail scams, providing an "extra line of defense" for preventing users from getting caught up in e-mail identity- and information-theft scams, MacGregor said.

Improvements to the user experience in Thunderbird 1.5 include auto-saving of e-mails in progress as drafts and automatic spell-checking as an e-mail user types a message. MacGregor also noted that the new automatic updating feature of Thunderbird 1.5 will make users particularly happy, since it means they don't have to keep checking back at the Mozilla website for the periodic stability builds the Thunderbird team provides for the e-mail client.

"Before you’d have to hear there was an update, or on your own periodically check and see if there's a new product release," he said. "Now we'll let you know." Mozilla also added automatic software updating to its popular Firefox browser in the last release of that offering, Firefox 1.5.

Thunderbird 1.5 also has new support for podcasting, as well as improvements to how the client deals with RSS feeds. Thunderbird 1.5 allows users to access podcasts via a dialog box that provides access to a "helper" application such as a web browser or audio player. The e-mail client can detect whether the podcast is an audio or video file and will play it using the correct player on a user's computer, MacGregor said.