Shiva Ayyadurai sued news website Tech Dirt earlier this year after it published several articles denying his claim.

The judge overseeing the case said email was impossible to define precisely, meaning Mr Ayyadurai's claim could not be proven.

Mr Ayyadurai said he planned to appeal against the decision.

Legal costs

Mr Ayyadurai's controversial claim revolves around a program he wrote in 1978, called EMAIL, that was used by staff at the University of Medicine and Dentistry of New Jersey. He was granted a copyright for this program in 1982.

Many news websites have published detailed rejections of his claim.

Tech Dirt was one of the most vocal critics of Mr Ayyadurai's campaign to establish his software as the definitive version.

Technology history suggests that modern email programs have a lot of influences, but much of the work was done prior to 1978 by many different developers.

Ray Tomlinson is widely acknowledged as the programmer who, in the early 1970s, first used the "@" symbol as a way to describe a particular user on a particular network.

Mr Ayyadurai said Tech Dirt had libelled him, inflicted emotional distress and harmed his ability to make money from his accomplishment. He sought $15m (£11.5m) in damages.

The judge disagreed and said in his ruling that because the history of email was in doubt, questioning Mr Ayyadurai's claim to be its inventor was not libellous.

Tech Dirt said it was "pleased" with what was a "big win" for free speech.

But it was "disappointed" with one aspect of the ruling, in which the judge said it would have to pay its own legal costs.