The Postbox e-mail program starts with the free Thunderbird program and adds a bevy of nice features--as well as a $40 price tag after the free trial.
Postbox's many features are designed primarily to improve searching and organizing our often out-of-control inboxes. It also ties into popular online services such as Picasa Web Albums and Facebook.
If you've used Thunderbird in the past, Postbox will look familiar; Scott MacGregor, who worked on Thunderbird for a decade, is now working on Postbox. You'll see a similar toolbar of icons up top with a folder and account list on the left, while the right-side sports the message list and preview pane.
But you'll also quickly notice where Postbox differs from Thunderbird. For starters, it's easier to find what you want. Buttons for Attachments, Images and Links located in the upper-right allow you to bring up lists or thumbnails of each item type. You can also search for messages based on assigned topics, date sent, sender, or other criteria.
Postbox organizes what you see. The program gathers a message and all of its replies together into a collapsible message thread, and also uses tabs to display contacts, opened e-mails and topic views, which are Postbox's version of Thunderbird tags. Although the new app can still use traditional folders to sort messages, it emphasizes assigning these 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 those 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 find some of the ways that Postbox integrates with online services. For example, clicking a Find Images icon allows you to search for a picture in a Picasa Web album (as well as in your e-mails), and then drag-and-drop that picture into your e-mail. Other tie-ins allow for uploading an attachment to Google Docs, sending a link to your Del.icio.us account, or displaying a Facebook friend's picture next to his e-mails (a small but surprisingly enjoyable feature).
Postbox can quickly pull messages in from a Gmail, Yahoo Mail Plus, or other POP3 or IMAP-accessible account. One nice touch: Postbox defaults to leaving the messages on the server for POP3 access, so that you won't accidentally leave yourself able to read 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.
While Postbox lacks a built-in calendar, it does support the popular Lightning calendar add-on for Thunderbird, along with a handful of other add-ons. Postbox maintains a list of currently compatible add-ons.
Postbox offers plenty of fun and useful features, but unlike its Thunderbird base, Postbox isn't free. Its $40 cost for a single-user license may be worth it for business users who aren't tied to Outlook, or for home users with large inboxes who want all the bells and whistles. But casual e-mailers will likely be content to stick with Webmail.