United Online Inc. has sold off its last social media business to a German company in a deal valued at about $18.3 million. The Woodland Hills Internet service and social-media company had operated StayFriends websites in five European countries. The buyer, Ströer Content Group GmbH, provides out-of-home and online advertising services. United Online Interim Chief Executive Jeff Goldstein said the sale is consistent with the company’s strategy to exit social media. In August, United Online sold its Classmates.com business for $30 million to Intelius Holdings Inc., in Bellevue, Wash. “We believe this outcome is another step towards our goal of maximizing shareholder value through our ongoing evaluation of strategic alternatives with JMP Securities,” Goldstein said in a prepared statement. JMP, in San Francisco, was retained in November to conduct a strategic review, including a potential sale of the company or its assets. Closing on the transaction between United Online and Ströer is expected by the end of the month. United Online announced the divestiture late Thursday. Shares closed Friday down 8 cents, or a fraction of a percent, to $11.46 on the Nasdaq.