Yahoo has announced their latest developer platform, the Yahoo Mail web service. John Kremer, vice president for Yahoo Mail, told WebProNews he hopes to see developers leverage Yahoo Mail’s 250 million users to build innovative and interesting applications like the Flickr postcard created during their Hack Day event last September.Yahoo Developer Network leader Chad Dickerson also disclosed an extra incentive for approved developers. Applications that drive new members to the premium service, Yahoo Mail Plus, will earn the developer ten dollars for each referral who joins. Developers building applications for Yahoo Mail Plus will have access to the full set of features available through the API.