If you’re looking for a lightweight email client for POP- or IMAP-based mail, or if you’re looking to get away from the security concerns inherent in Microsoft Outlook Express, look no further than Mozilla Foundation's Thunderbird 1.0, a free, open-source email client that’s available from Mozilla's Web site as a 5.8MB downloadable .exe file.

The installation process is quick and painless. (If you have Firefox installed on the same system, the installation process automatically integrates Thunderbird with Firefox’s Tools, Read Mail option.) After you complete the installation, Thunderbird prompts you to import your previously established email settings and make Thunderbird your default mail reader. Thunderbird supports importing mail from Outlook Express, Outlook, Netscape Communicator 4.0, and QUALCOMM's Eudora.

In my test, the import process successfully imported all the messages from my Outlook Express installation but failed to import the newsgroup accounts and message filters I'd configured. Thunderbird has its own built-in spam filter that uses whitelist, blacklist, and Bayesian filters to eliminate unwanted junk mail. The program had no problem using POPFile, the open-source antispam filter that I used in Outlook Express, and the import process correctly imported all the account settings.

If you’re familiar with Outlook Express, Thunderbird will feel quite intuitive. Thunderbird has a similar look and feel, and adapting to it was effortless. I prefer this UI, which Figure 1 shows, to that of Eudora or the other POP email clients.

Thunderbird's feature set also rivals that of Outlook Express. Like Outlook Express, it can connect to multiple mail servers, and it supports reading newsgroups. It has a built-in spell-checker. You can reconfigure the UI to switch the positions of the frames, and you can even turn off the preview pane. For more secure email content, Thunderbird supports Secure MIME (S/MIME) and message encryption. Other Thunderbird features go beyond Outlook Express's offerings. In addition to Windows, Thunderbird also runs on Apple Computer's Macintosh, Linux, OS/2, and Sun Microsystems' Solaris systems.

Another impressive feature is Thunderbird’s built-in RSS reader. Like its cousin Firefox, Thunderbird is extensible via a plug-in architecture. You can install Thunderbird’s extensions using the Tools, Extensions menu option. A handy extension is the Sunbird Calendar (, which lets you schedule events.

One notable missing feature in Thunderbird is online Help. The Help link simply takes you to the Mozilla Web site. Despite minor misgivings, such features as the built-in RSS reader and calendar give Thunderbird some nice advantages over Outlook Express. However, the lack of complete import capabilities might be a stumbling block to advanced Outlook Express users.

Mozilla Thunderbird 1.0
Contact: Mozilla Foundation
Price: Free
Pros: Boasts an easy-to-use interface, lets you import messages from all the popular POP email programs; includes a built-in RSS reader
Cons: Offers no online help; won't import Microsoft Outlook message filers or newsgroups
Rating: 4 out of 5
Recommendation: Thunderbird is a full-featured, user-friendly POP3 and IMAP email client that's a suitable replacement for Outlook Express or Eudora.
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