Pitney Bowes Inc. has filed suit against Zumbox, alleging the Westlake Village start-up’s “paperless mail” service infringes on its patents.

Pitney Bowes, a Stamford, Conn. public company, is best known for its postal scales but has expanded into online communications products and invested more than $200 million in research and development in 2008 alone, according to a press release. The lawsuit filed Tuesday in California Central District Court contends that Zumbox, a private equity-backed company now testing its product in San Francisco and other markets, is infringing on three of its patents.

Zumbox Chief Executive Donn Rappaport said in a statement issued Wednesday that his company would vigorously defend its Web-based platform for the delivery of paperless mail. The service allows online messages to be sent to subscribers based on their street addresses. The goal is to provide an alternative to paper mail.

“We are confident that Zumbox is not in violation of, or infringing on, Pitney Bowes’ patents in any way,” Rappaport said. “We are just now reviewing the suit to better understand their motives.”

Founded in 2007, Zumbox has raised about $12 million from investors that include Michael Eisner, founder of Tornante Co. and former chief executive of Walt Disney Co., and Bill Guthy, founding principal of Guthy-Renker.

Pitney Bowes has a market cap of $5 billion.