Postbox starts with the program code and adds a bevy of features designed primarily to improve the search function and message management. If you've used Thunderbird, Postbox will look familiar. You'll see a similar toolbar on top, with a folder and account list on the left. The right side consists of the message list and preview pane.
But you'll quickly notice where Postbox differs, too. Postbox's creators, including Scott MacGregor, who worked on Thunderbird for a decade, know that much of users' frustration with e-mail stems from not being able to find items quickly. So Postbox offers such features as an Attachments button, which you can click to view a list of all your attachments, and an Images button, which lets you see a thumbnail presentation of all your e-mailed images.
Postbox uses tabs--its version of Thunderbird tags--to display those views, as well as to show individual messages and topic views. While the new app can still use traditional folders to sort messages, it emphasizes assigning topic keywords instead. You can assign a topic to a message, and then view all items with that topic by clicking on a virtual folder on the lower left. Topics will likely prove most useful to anyone who is willing to go whole hog and forgo folders in favor of the versatile tags.
While composing a message, which still happens in a separate window, you'll encounter some of the ways that Postbox integrates with online services. For example, you can click a Find Images icon that allows you to search for a picture in a Picasa Web album (as well as your e-mail), and then drag and drop that picture into your e-mail. Other tie-ins allow you to upload an attachment to Google Docs, for instance, or to send a link to your Delicious account without leaving Postbox.
Postbox can quickly pull in messages from a Gmail, Yahoo Mail Plus, or other POP3 or IMAP account. One nice touch: It defaults to leaving the messages on the server for POP3 access so that you won't accidentally limit yourself to reading your e-mail only in Postbox. It will also prompt you to import your e-mail, settings, and contacts from Outlook, Outlook Express, Thunderbird, or Eudora if it finds one or more of those programs on your computer.
Postbox offers plenty of useful features that might entice you to give it a whirl. Unlike the open-source Thunderbird, however, Postbox is made by a for-profit company. Though Postbox's makers haven't yet decided on a business model, they may elect to charge for the program when they release a final version, perhaps sometime in the spring.