Postbox is a new cross platform e-mail client for Windows and Mac computers. It's an alternative to Microsoft Outlook, and manages to bring some of the benefits of Web e-mail to a desktop application.
Things like a conversation view, tagging, and search that indexes both mail and attachments are all features Gmail users have been enjoying for years. The problem is, those features and several others have not gone over to the desktop side of things without additional software plug-ins from third-party providers.
Postbox answers that by taking many of these single features sought after by other third-party developers and blending them into a standalone client. For example, if it sees an address it will pull up a quick map link complete with business information. When you're offline you still get this information.
As some of the session judges at the TechCrunch50 conference noted, some of the things this product does would be much better suited as an extension to the software e-mail client you're already using. I'd certainly love the photo browsing client and conversation view in my Outlook, but I definitely can't ditch it until this product gets rock solid Microsoft Exchange support with a built-in calendar (a feature the product does not have).
Postbox currently works with IMAP, POP, and SMTP protocols, letting you tie in your Web mail accounts. Unless your business is running off Google apps this probably won't be a good companion for anything besides your personal accounts. That said, compared with something like Apple's Mail application, it looks like a nice step up.
Update: Postbox will be available for download in "a few weeks" time. Only the sign-ups were opened up today. I've also thrown in another screenshot after the jump.