Company officials said that Gross, who headed up all of the company's wireless initiatives, wants to spend more time with his family.
But sources close to the situation said that Gross was encouraged to leave because various initiatives in the wireless division haven't taken off as quickly as some thought they should.
The Mobile Information 2001 Server, better known as "Airstream," was supposed to be a broad-based middleware platform that would provide wireless access to multiple devices in multiple formats, but the first edition supported only WAP (Wireless Application Protocol).
The Microsoft/Qualcomm wireless middleware server spin-off Wireless Knowledge competed with Airstream, and licensing agreements between Wireless Knowledge and Microsoft were confusing.
Wireless Knowledge supports a broader array of devices and applications, whereas Airstream is limited to just Exchange at present.
On the device side, US carriers have yet to adopt the much-touted smart phone platform known as "Stinger."
Prior to his current position, Gross was senior vice president of Microsoft's Collaboration and Mobility Group, and before that the vice president of the Developer Tools Division.
He joined Microsoft in 1996.
