Yahoo is set to allow outsiders to create new services using the world's most popular consumer email program, in the broadest move the Web has yet seen to enlist independent programmers to build a company's products for it, a Reuters report said.

The reuters report said officials of the world's largest Internet media company planned to give away the underlying code to Yahoo Mail, one of the crown jewels of its business, in a bid to encourage software developers to build new applications based on email.

The move to open up the underlying code of Yahoo Mail, used by 257 million people, is designed to spark development of thousands of new email applications built not only by Yahoo engineers but by outside companies and individuals.

Chad Dickerson, head of the Sunnyvale company's software developer relations program, was quoted as saying that he believed that the open approach to programming represented the biggest single Web software ever to be opened up for public development.

Software developers have traditionally kept careful control of the underlying programming code of their products and allowed outsiders to make only incremental improvements. In recent years, Web developers have opened up that process to encourage outsiders far deeper access to the underlying code, the Reuters report said.