At the 3GSM World Congress in Barcelona, Spain today, Microsoft put the final piece of its mobile messaging strategy into place—officially joining an increasingly crowded (RIM, Visto, Good Technology, Nokia - with new subsidiary Intellisync - Seven, etc.) and lucrative field.

Software's 800-pound gorilla released the wireless messaging-centric Exchange Server Service Pack 2 (SP2) last fall. The update featured push e-mail technology. So when the server receives messages, they're automatically sent to a mobile device instead of the user having to manually pull them down himself, or schedule retrievals at set intervals.

While this service has been available on the backend for some time, it wasn't until 3GSM that end-users finally found out when their smartphones could take advantage of that capability.

A number of Microsoft's carrier partners - Cingular Wireless, Orange, T-Mobile, Vodafone, among others - will offer free Direct Push (the client enabler) upgrades for their subscriber’s Windows Mobile 5.0 devices. While Palm and iMate said they would update their current Windows Mobile devices - the Treo 700w in Palm's case.

Several new Windows Mobile devices to be unveiled Monday will support Direct Push too. These include Hewlett-Packard's highly-anticipated iPAQ hw6900 Mobile Messenger, the Gigabyte Communications g-Smart (offered by Chunghwa Telecom Co. Ltd. in Taiwan), the ASUS P305 3G-enabled smartphone, and the Fujitsu Siemens FS Pocket Loox.

Taiwanese original design manufacturer High Tech Computer, the company behind some of the most commonly found Pocket PC Phones on the market, also has a slate of Direct Push-enabled Windows Mobile devices on tap for delivery to carriers next quarter.

To further its mob-e-mail plans even more, Microsoft added Direct Push to Windows Small Business Server and some operators will start offering it as a hosted service, starting with T-Mobile in Europe.

Cingular will deliver Direct Push to its new 8100 series Pocket PC Phones and 2125 Windows smartphone (both of which we'll be reviewing this month) during the first half of the year. T-Mobile has two new Microsoft-based smartphones, the MDA and SDA, on the way for the U.S. market also.

T-Mobile's executive VP of international business marketing Andre Star says Microsoft messaging solutions complement the carrier’s "successful suite of Microsoft-based solutions with a compelling messaging product that addresses these critical business needs while delivering mobile professionals much more than simple mobile e-mail. In alliance with Microsoft, we have an opportunity to strengthen our business customer portfolio and deliver another very powerful mobile business solution."

Interestingly, DataViz last week released RoadSync 2, its Exchange Server ActiveSync enabled client for Symbian smartphones; bringing Redmonds's push technology to one of the company's chief smartphone competitors a hair before its own Windows Mobile platform. Microsoft also announced a licensing deal to deliver wireless ActiveSync, including push e-mail to Sony Ericsson's upcoming P990 and M600 Symbian phones.

As even RIM learned - in spite of the success of its BlackBerry handhelds - users and especially enterprises prefer choice. To succeed over the long haul, a mob-e-mail platform should support more than a single type of device.

And while Microsoft's Windows Mobile platform is ascendant and Symbian's share is slipping (hovering around 51 percent right now, but expected to drop to less than half that number by decade’s end, according to The Diffusion Group), they're going to be fighting over a skyrocketing market: growing from tens of millions to well over a hundred million devices shipped per year in only a couple of years.