With the launch of its new Treo 755p this week, Palm is taking a converged approach to the smartphone, using the Palm OS the company originally built its success upon but incorporating the Microsoft push e-mail technology in a nod toward the fast growing e-mail market.

The approach combines two strategies the handheld maker had previously pursued. For the last two years, Palm has been making separate Treos, alternately using the Palm OS and Microsoft’s Windows Mobile. In fact, Palm announced earlier this year it plans to upgrade to its Windows smartphone line to Windows Mobile 6.0 in conjunction with the launch of an HSDPA-powered Treo.

The new 755p seeks to capture both audiences, based on its core OS but using Microsoft ActiveSync technology e-mail support and Outlook so the device can link directly to Exchange servers. The enterprise has been the hottest growing area for smartphones, driven by e-mail applications. Palm has sought to tap into the market with its recent purchase of Good Technology, but all third-party e-mail solutions require software upgrades on the server side, including Good, as well as service contracts with push e-mail provider. The ActiveSync and Microsoft Direct Push technology, however, allows an enterprise to integrate the phones directly with its existing exchange infrastructure. Microsoft also has an advantage in that its ActiveSync software is automatically licensed with Exchange so companies adopting the mobile platform don’t pay any additional licensing fees.