CMGI Inc has bought email direct marketing company Yesmail Inc in a stock-for-stock transaction worth roughly $500m. CMGI is best known these days as a large-scale internet incubator. Other recent acquisitions include instant messaging expert Tribal Voice Inc, ad marketer FlyCast Communications Corp, online ad network AdForce Inc and ad tracker Adknowledge Inc. The company seems to be bulking up its web advertising and marketing properties ahead of an assault on market leader DoubleClick Inc. One of CMGI’s core strengths is providing comprehensive interactive marketing solutions, explained yesmail CEO Dave Tolmie, and yesmail.com’s business is extremely complementary to this focus.