SAN JOSE, Calif. - Visto Corp., a maker of mobile e-mail technology, 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 a permanent injunction to stop the infringement, was filed late Wednesday — the same day Visto announced that NTP Inc. had acquired an equity stake in the company and signed a patent licensing deal.

Visto's allegations against Microsoft and its Windows Mobile 5.0 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.

"Windows Mobile 5.0 is an infringement of Visto's intellectual property of a technology that our firm created, patented and successfully sells on the market today," Visto CEO Brian Bogosian said Thursday.

Jack Evans, a Microsoft spokesman, said the company has not completely reviewed the complaint and will not comment on it until it has done so.

"Microsoft stands behind its products and respects intellectual property rights," he said.

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 to 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.

Shares of Microsoft fell 17 cents to close at $26.92 Thursday on the Nasdaq Stock Market.