Microsoft on Tuesday released the second beta of the first service pack for Exchange Server 2007, plugging two holes in the process that prevented users from integrating with Vista and Windows 2008.

The beta, however, does not address the fact that the 64-bit-only Exchange Server 2007 cannot be virtualized on Microsoft’s current Virtual Server 2005 R2 platform, which only supports 32-bit guest operating systems.

Microsoft also added to the service pack cluster replication features, mobile device synchronization options and voice and fax integration via Office Communications Server 2007.

Virtualization, therefore, remains the biggest hole. Users have called the incompatibility between the messaging server and the virtualization platform “a dreadful mistake” given that Microsoft competitor and market leader VMware supports Exchange 2007 on its virtualization software.

Microsoft said in January that is would consider adding virtualization support in SP1 if there was user demand. Microsoft has a 32-bit version of Exchange 2007, but it is available only for testing purposes and Microsoft has no plans to change that.

“Given that the highest demand for virtualization of Exchange Server currently comes from building out sandbox, testing, training and demonstration environments we made the decision to release a 32-bit trial experience to meet these needs,” said a company spokeswoman.

Microsoft said Exchange Server 2007 SP1 beta 2 is feature complete and is what users will get when the final code ships between Oct. 1 and Dec. 31.

Without virtualization support in SP1, users will have to wait until the Windows Server Virtualization add-on for Windows Server 2008 ships next summer.

The beta 2 of SP1 is being made available to nearly 1million users via TechNet and Microsoft Developer Network. The first beta, released in March, was made available to 150,000 users.

Microsoft does not plan to have a public beta before final release of the code.

With beta 2, Microsoft has added integration between the Exchange Management Console and Vista. Previously, users could not run those management tools on Microsoft’s newest operating system. In addition, those tools also can run on Windows Server 2008 starting with SP1.

Integration with Windows Server 2008 will also deliver IPv6 support to Exchange, and lets users deploy multiple sub-nets when setting up continuous cluster replications. Previously, users were required to run the replication on one subnet which could cause latency and security issues.