The U.S. Postal Service has given a federal appeals court affidavits from 18 private firms supporting the agency's efforts to maintain its controversial new electronic mail system that the Justice Department is trying to shut down.

The Postal Service filed a 69-page brief with the U.S. Court of Appeals for the District of Columbia supporting its contention that the electronic mail service was approved properly by the independent Postal Rate Commission before the service started last Monday.

The Justice Department contended in papers filed with the appeals court earlier this month that the Postal Service refused to participate in hearings and went ahead with the service without a recommendation from the rate commission.

The rate commission earlier recommended an experimental electronic mail service, but the appeals court said last May that the commission didn't have the authority to determine whether the service was experimental or permanent.

The rate commission then began expedited hearings on whether E-COM should be permanent, but the Postal Service refused to participate, saying the commission didn't have the authority to determine the issue.

The Postal Service contends the May appellate court decision meant the judges approved the start of electronic mail but only disputed the rate commission's authority to make it experimental.

The Postal Service also said in a brief that the court doesn't have jurisdiction over the case because the Justice Department didn't exhaust all administrative remedies.

The Justice and Commerce departments as well as private telecommunications firms have said the service unfairly prohibits private firms from entering the electronic message delivery business.

Affidavits ranged from Merrill Lynch, Pierce, Fenner & Smith Inc. to Better Business Communications of Falls Church.

Under E-COM, large-volume mailers send messages from their computers to computers in 25 post offices around the country. The messages are supposed to be printed, stuffed in envelopes and delivered in less than two days.

So far more than 100 companies have signed up for the service.

Supporting the Justice Department position were responses from Graphnet Inc. and GTE Telenet Communications Corp., two telecommunications firms, and a friend-of-the-court brief from the Postal Rate Commission, a Justice Department spokesman said.