The next big thing in electronic billing may be e-mail.

Transactis' chief executive, Thomas Kohn, said that a New England utility has tested his company's BillMail service - and that a top-five card company, a top-10 utility, and a top-five telecom plan to begin using it during the first half of 2006.

In the Transactis system, consumers enroll on a Web site they need not visit again. They pay e-mailedbills by entering a username and password each time.

Ron Averett, Princeton eCom's chief executive, said e-mail "is just another form of presenting content and executing payment, just like the biller-direct model and just like the aggregation model."

He said that it takes 60 to 75 days to implement the system with a customer, and that the concept has proved appealing to billers.

In Transactis' BillMail service, the payments are processed through Transactis or the billers' current billpay vendor. Eric Fox, the company's vice president of business development, said that if criminals learned a BillMail username and password, all they could do with them is pay the consumer's bills.

"A bill paid via BillMail is safer than one paid through any other channel, including paper," he said. "All financial data is held securely and separately."

Gwenn Bezard of Aite Group LLC says e-mail billing "is very attractive - but the devil is in the details."

Mr. Bezard said e-mail bills could eventually match or beat online bill payment sites in popularity with billers.

"Billers, especially in some verticals like utilities, are growing frustrated with the level of adoption of bill payments on their Web sites" and may be eager to consider an e-mail alternative, he said.