Microsoft, Yahoo, AOL, and others used the second annual summit to highlight adoption of sender authentication technologies and talk up their schemes for verifying e-mail senders and recipients. But some messaging experts complain that there are still too many competing authentication schemes to prevent technical conflicts and guarantee widespread adoption of e-mail authentication.

The second annual event, with the theme "Summit II -- Authentication & Reputatio-Building Online Confidence" was intended to highlight advances in the use of e-mail authentication technology after a year in which discussion and debate about it has faded.

Microsoft used the conference to promote adoption of the Sender ID, its e-mail authentication architecture, and to introduce "Smart Network Data Services," spam reports generated by the company's MSN and Windows Live services, and "MSN Postmaster Services" a new program to provide tools and best practice guidance for ISPs to manage their e-mail infrastructures with MSN and Windows Live users.

Sender ID increased threefold from 7 percent in July 2005 to 21 percent among Fortune 500 companies, said Craig Spiezle, director of technology care and safety at Microsoft.

Currently, about 32 percent of all e-mail sent is Sender ID-compliant, Spiezle said.