John Payne's departure comes three days after Stamps.com's president, chief financial officer and comptroller stepped down. Marvin Runyon, the former U.S. Postmaster General, has taken over for Payne, who has been with the online postage company since 1998.
Santa Monica, Calif.-based Stamps.com said its board of directors, acting with the company's remaining executive team, will guide the company until a new chief executive is found. The search for Payne's replacement will begin immediately.
The market for online postage services, like many Internet-related businesses, has taken a beating on Wall Street. Shares of Stamps.com have languished since the early part of this year, when they reached an all-time high of $98.50.
But Stamps.com maintained in a statement that the company is in a strong financial position.
"Our sound financial standing of $300 million of cash-on-hand provides us the resources to accomplish our business objectives and remain the category leader," the company said.