By far the most mature e-mail client in this roundup, Microsoft Outlook 2003 offers a slew of options and features that will appeal to both business and personal users. Outlook also aptly serves as a personal information manager, with first-rate calendar and address book features. Meanwhile, tight integration with Microsoft Office 2003 makes it an invaluable collaboration tool.

The latest version of Outlook has an improved multipane view. Tabs let you roll up (or clump) messages by sender name; day, month, or week received; message size; and so on. And perhaps the most useful little gem new in Outlook 2003: If you are working in another application, a small window appears when you receive a new message. It displays the subject and first line of the message, along with options to flag, delete, or open the message (without having to switch over to Outlook), then fades out.

Outlook 2003 also boasts a revamped spam filter that does a much better job of blocking junk than Outlook 2002 did. Still, compared with the dedicated spam blockers in this story, Outlook 2003 was mediocre, rarely misidentifying good mail but missing a lot of our spam.

Other security features, such as blocking images and HTML, are easy to define. By default, remotely linked images in messages do not appear, but with a single click on an HTML message we could download images or change settings to permit image downloads from safe senders and trusted Web sites.

Some of Outlook's features could still stand improvement. For instance, we're growing tired of waiting for a better and faster search tool. But even with its shortcomings, Outlook 2003 is undoubtedly the king of e-mail clients.