He said there are potentially tens of millions of business users, compared with 8 million to 10 million who are using systems from RIM, Good Technology Inc. and others.

Technologies from RIM and others often require an additional and costly e-mail server, Starkweather noted.

About 100 carriers currently support Microsoft's Direct Push, Starkweather said, but only four were named, including one major U.S. carrier, Cingular Wireless LLC. The others were Orange, T-Mobile and Vodafone Group PLC. All four announced free upgrades to customers of Windows Mobile 5.0, which enables Direct Push. Microsoft made its announcement on Monday at the 3GSM Congress. Windows Mobile 5.0 was announced last May, with Direct Push and MSFP functions announced shortly afterward.

"The carriers are reacting to a business opportunity, since they realize they have tens of millions of business customers, all potentially interested," Starkweather said.

In addition to the four named carriers, Microsoft said Palm Inc. and I-Mate reaffirmed commitments to MSFP upgrades, according to a Microsoft statement. And four new Windows Mobile-based devices were unveiled, which ship with Direct Push technology.