Updated

Mobile e-mail startup Visto Corp. has sued Microsoft Corp. for allegedly infringing on three of its patents related to how information is handled between servers and handheld devices such as cellular phones.

The lawsuit, which seeks unspecified monetary damages and an injunction barring the sale of products, was filed late Wednesday — the same day Visto announced that NTP Inc. had acquired an equity stake in the startup and signed a patent licensing deal.

Visto's allegations against Microsoft are similar to NTP's against Research In Motion Ltd., which now faces the possible shutdown of its popular BlackBerry messaging service in the United States.

"For their foray into mobile e-mail and data access, Microsoft simply decided to misappropriate Visto's well known and documented patented technology," Visto CEO Brian Bogosian said in a statement.

A Microsoft spokeswoman did not immediately return a call seeking comment on the suit. In a recent regulatory filing, the software company said it is a defendant in more than 35 patent infringement cases "that we are defending vigorously."

Visto claims Microsoft, as portable devices handle more e-mail, is making matters worse by bundling its Windows Mobile operating system with its market-leading Exchange e-mail server.

"This method of bundling software has led Microsoft to be prosecuted by competition authorities in the past, and in this case, potentially increases the rate and manner in which their infringement on Visto's patents occurs," the company said.

NTP's deal with Visto also could help it bolster its case against RIM as it can now say it is more than a company that just holds patents and litigates to enforce them. Under the agreement, Visto will have access NTP's patent portfolio for the life of the patents.

"This is a clear win for mobile email users everywhere as it provides them with a viable alternative to RIM that protects them from any NTP litigation risk," Donald E. Stout, NTP's co-founder.

Visto, based in Redwood Shores, Calif., said its clients include Cingular, Sprint-Nextel, the Vodafone Group and Rogers Wireless. It has more than 300 employees and holds 25 patents.

The lawsuit was filed in the U.S. District Court in Marshall, Texas.