The terms of the deal were not disclosed.
Lansoft, based in Columbus, Ohio, brings about 690 corporate customers to Mail.com, which is hoping the acquisition will also help to boost its technical presence in the corporate messaging arena.
"This transaction is consistent with our strategy to acquire companies with a complementary business to business team and established customer base to accelerate our penetration of the business messaging market," Gerald Gorman, Mail.com's chief executive, said in a statement.
Mail.com provides email services for consumers through several partner Web sites, including CBS SportsLine, NBC and Snap.com. CNET, the publisher of News.com, is an investor in Snap.com.