Cisco is buying PostPath, a maker of e-mail and calendaring software, for $215 million and plans to add those capabilities to its on-demand Web Ex Connect collaboration platform.

PostPath makes PostPath Server, an e-mail and collaboration server the company touts as a replacement or supplement to Microsoft Exchange.  An archiving edition of the software is available to store e-mails in a less cumbersome fashion than Exchange does with its journaling of old e-mails. The company also offers a version of PostPath Server for VMware. (Watch a slideshow of the hottest M&As of 2008.)

Cisco plans to put the server in the cloud and sell an e-mail and calendaring service to its customers. "Our 'cloud-based' delivery model offers our customers rapid deployment and compelling economics," says Doug Dennerline, senior vice president of Cisco's Collaboration Software Group (CSG).

PostPath is all about requiring no middleware to interoperate with Microsoft Outlook, Exchange, Active Directory, ActiveSynch and BlackBerry Enterprise Server, among other applications. But it also promotes itself as a Linux-based replacement for Exchange that gets around some of the Microsoft platform's shortcomings, including larger data stores and higher performance in terms of how many hits per minute the platforms can handle.

Cisco bought WebEx last year to deliver software-as-a-service (SaaS) offerings, including instant messaging, team spaces for collaboration, wikis and document sharing.

Privately held PostPath was founded in 2003.

Cisco says it expects to close the deal by the end of October and add PostPath's 67 employees to its Collaboration Software Group. CSG is part of Cisco's recently established Software Group that oversees the IOS network operating system, network and service management, unified communications, policy management and SaaS offerings.