The Internet Engineering Task Force (IETF) has wound up its working group on Sender ID, the proposed spam-cutting standard.

The purpose of Sender ID technology is to help verify the source of emails by authenticating domain addresses as valid.

It was a combination of Microsoft's Caller ID and the Sender Policy Framework originally put forward by Meng Wong, chief technology officer at Pobox.com.

The working group MTA Authorisation Records in DNS (Marid) had been given the task of overseeing the creation of an agreed Sender ID standard.

But in an email to members, the IETF's Ted Hardie said: "The group remains divided on very basic issues.

"After an assessment of the current state of the [Marid] group, its charter and its milestones, the working group chairs and area advisor have concluded that the [Marid] group should be terminated.

"The working group chairs and area advisor are agreed that the working group has no immediate prospect of achieving its primary milestone."

The closure of Marid reflects the potential conflict between code issued under the open source licensing model and patented intellectual property (IP), because the proposed technology included two Microsoft patents.

Open source companies the Apache Software Foundation and Debian complained that Microsoft's royalty-free licence was incompatible with open source.

According to John Collins, a partner at law firm Marks and Clerk, licences for internet-related technologies must be royalty free and non-discriminatory - effectively open to all.

"There is always a tension between IP and open source. This is one example of Microsoft defending its patch but, when it's internet, the standards body is looking for complete openness," he said.

Microsoft had not commented at time of going to press.