July 30, 2008

PostPath cracked Exchange protocols for Postfix-based mail server

Author: Tina Gasperson

PostPath is a drop-in Microsoft Exchange alternative based on the open source Postfix MTA. PostPath director of product management Sina Miri calls PostPath the "only" drop-in Exchange replacement, and he says that ability is the reason why his company makes PostPath available only with a proprietary license, despite its open source roots.

Miri charged PostPath engineers with creating a mail server that was comparable to Exchange, but was less expensive, more flexible, and able to run on Linux servers. Not only that, but PostPath needed to be compatible with Microsoft Exchange, meaning that the network had to work with PostPath with no plugins, add-ons, or rewritten protocols. Miri says PostPath accomplished its goals by building PostPath from Postfix, the popular MTA created by Wietse Venema and distributed under the terms of the IBM Public License (IPL), but with a crucial addition.

The pièce de résistance in the creation of PostPath was the compatibility component. "There is no plugin or middleware required to use PostPath," Miri says. "When you drop PostPath in, the network thinks it is talking to an Exchange server. This makes it very easy for people to evaluate and buy and migrate. It's a lot easier to go from Exchange 2003 to PostPath than to go from Exchange 2003 to Exchange 2007. That's like doing a completely new installation." Microsoft calls migration from Exchange 2003 to 2007 a "transition" that happens in "several phases." In contrast, PostPath's claim to fame is that it uses Exchange's own protocols to achieve full compatibility even with other Exchange servers on the network, making it possible for Exchange 5.5 or 2003 users feeling the squeeze from Microsoft to easily move to an alternative mail server infrastructure.

Gartner analyst Matt Cain says PostPath really does drop into the network. "They can fit nicely in Active Directory, and that's one of the primary things folks are concerned about. I don't know about the [ease of] migration, but I would say that it is pretty difficult to migrate from Exchange 2003 to 2007, so it wouldn't be all that hard to make it easier [with PostPath]."

Exactly how PostPath was able to unlock Microsoft's protocols will remain a secret, because PostPath is proprietary. "If you give that away, a lot of the value of PostPath is going away," Miri says.

Postfix author Venema doesn't express any angst over the fact that a proprietary product borrows so liberally from open source. "They can do what they want to with their own source code," he says. PostPath's modifications to Postfix and other open source code are posted at the company's Web site for free download.

If Microsoft has a problem with PostPath reverse-engineering its protocols, it hasn't told PostPath, Miri says. Microsoft officials declined to comment when asked if they minded. But PostPath is extra careful never to hire anyone who has worked at Microsoft before, "so there's no risk of somebody thinking we came by it unfairly."

Basing PostPath on open source has been good for the company, Miri says. "You get better support from using open source tools than with commercial products. If you come across some issues or questions, if you use open source there's more information available to you much faster than using a commercial product. I don't see how a company even as big as Microsoft can compete with the service and support [from open source products]."


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