Microsoft are back in the courts again, this time facing down with Mobile technology company Visto Corporation who has filed a patent infringement lawsuit against Microsoft for alleged misuse of Visto's mobile e-mail technology. The company contends that Microsoft has knowingly infringed on three patents that they hold, concerning proprietary technology which enables users to access e-mail and other data from their mobile devices. The company claims that they developed and patented this technology a decade ago, and that Microsoft's Windows Mobile 5.0 is a blatant infringement on this patented technology.

Visto claims that Microsoft's bundling practices only make matters worse. By bundling its Outlook e-mail server with Windows Mobile 5.0, Visto says, Microsoft multiplies the instances of infringement of Visto's intellectual property.

The suit, which is drawing comparisons to NTP's suit against Research in Motion, was filed in the US District Court for the Eastern District of Texas.