Mobile e-mail and calendar vendor Visto has chalked up one legal win as it heads toward a patent-infringement trial against Research In Motion that is set to begin on Monday.

The U.S. Patent and Trademark Office (PTO) has validated 21 claims of a patent that RIM challenged after Visto sued the company for patent infringement in 2006. The patent, number 7,039,679, involves a technology for synchronizing e-mail between a mobile device and a LAN server. It was filed in 2003 and granted to Visto in 2006.

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Visto sells software that competes with RIM's push e-mail technology, which synchronizes e-mail to BlackBerry devices. In April 2006 it sued RIM, claiming the dominant mobile e-mail vendor had infringed four of its patents. Visto asked the U.S. District Court for the Eastern District of Texas for unspecified damages and sought to have RIM's network shut down.

Soon afterward, RIM countersued and asked for three of Visto's patents to be invalidated. Visto's original suit is set to go to trial on Monday.

Visto is no stranger to the courtroom. Shortly before it sued RIM, it won a $3.6 million award against rival Seven Networks in a similar patent suit. In March, the company settled a suit it had filed against Microsoft  concerning e-mail technology in Windows Mobile.