Crossbow, the Successor to Windows Mobile 5.0 will feature built-in IM, strong links with Office 2007, Microsoft's pending new office application suite and e-mail server. Crossbow will take aim at the Symbian and BlackBerry operating systems. The new OS for mobile devices from Microsoft will contain a new mobile version of Office Communicator, an Office 2007 enterprise communications application, that includes instant messaging on public and private networks, said Pieter Knook, senior vice president for the mobile devices and telecoms sector.

Knook said it's premature to say when Crossbow would be released, but that the company plans for an annual mobile OS release. Mobile operating systems are also complex since operators often must be tested to ensure their systems can work with a new OS, a six- to 12-month delay after a release, Knook said.

That process is nearly complete for the push e-mail capability of Windows Mobile 5.0, Microsoft's slow assault against BlackBerry e-mail that may now start to bear fruit. The company's new push e-mail capability depended on software upgrades on the telecom operators' side, as well as new versions of Exchange Server 2003 and Windows Mobile 5.0.

Microsoft is counting on strong connections with device manufacturers to strengthen its position with those enterprises already using Exchange but with a BlackBerry server. The new push e-mail feature would enable those companies to eliminate the BlackBerry middleware, which also consolidates their support structure, Knook said.