The U.S. Postal Service inaugurated E-COM, its long-awaited $40 million electronic mail delivery system, yesterday despite significant opposition from the Justice Department.

Postmaster General William F. Bolger called the new service a marriage of the Postal Service's delivery system with electronic transmission, and said that it is intended to propel the Postal Service from "moving the mail on horseback to stagecoach to ships to trains, trucks and airplaines" to the electronic age. E-COM "represents the latest step in a progression of technologies we have used to transport the mail," Bolger said.

E-COM nearly was stopped in its electronic tracks last week. The Justice Department attempted to have it halted temporarily, claiming that a proper hearing had not been held. The Justice and Commerce departments, as well as private telecommunications firms, have said that the service unfairly prohibits private industry from entering the business of delivering messages electronically.

However, the Justice Department was rebuffed by two federal courts last week in its last-minute attempts to stop E-COM.

"Naturally I am pleased that the district and appeals courts did not prevent this E-COM service from beginning," Bolger said at a press conference yesterday. "Further, we welcome a full hearing on the merits of our case. We believe we have proceeded fully within the law in obtaining approval to start this service."

To start the service, Bolger sent a message yesterday morning to all 25 E-COM post offices from the E-COM center in the old Post Office on Massachusetts Avenue. The message was delivered as a computer print-out on white bond paper tucked inside a white envelope with a blue stripe.

Under E-COM, large-volume mailers will 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 anywhere in the country in less than two days. So far, more than 100 companies have signed up to use E-COM, including Merrill Lynch & Co., Shell Oil Co. and Columbia Gas Systems Corp.

The service will cost mailers 26 cents for the first page and 5 cents for the second page, a $50 annual charge and a fee for each of the five telecommunications carriers that transmit messages to the post offices.

Bolger defended E-COM yesterday against complaints by public-sector and private-sector critics, saying that the service won't cost taxpayers money because it will pay for itself and that it won't prohibit private firms from entering the business.