New York--DoubleClick Inc. has agreed to buy NetCreations Inc., a manager of e-mail lists, for $191 million in stock. The deal was announced one day after NetCreations entered into a partnership with b-to-b specialist B2BWorks Inc., Chicago. New York-based NetCreations, which controls about 15 million opt-in e-mail names through its PostMasterDirect.com service, will give DoubleClick about 22 million e-mail names under management when the transaction closes. A day earlier, NetCreations entered a strategic alliance with B2BWorks, which will resell NetCreations' e-mail addresses to its network of b-to-b publishers. Privately held B2BWorks competes with DoubleClick's Sonar Network, a network of specialized e-mail newsletters.