Governors of the U.S. Postal Service yesterday ordered two steps designed to boost business at the nation's post offices.

To counter a long-term trend of declining parcel post volume, the Postal Service board proposed reduced rates for certain large-volume users. In addition, the governors also proposed some rate cuts for third-class bulk mailings.

And, looking to future years when more messages are expected to be transmitted by electronic communications facilities, the Postal Service board proposed an electronic message service similar to the current "Mailgram," but with cheaper rates.

Rate proposals to implement yesterday's decisions will be filed immediately with the independent Postal Rate Commission, which ordered sharp increases in postal rates earlier this year. The higher rates fueled concern inside postal management that a loss of business mail volume could accelerate, as users switched to private delivery businesses.

Postmaster General William Bolger told the board yesterday that the rate cuts are a "departure from the normal trend of recent years" but "the right direction to move."

He said the reduced rates are an effort to pass along price reductions where efficiency in handling large volumes of mail warrants such cuts. Postal officials said the reduced rates could lead to the handling of 30 million additional parcels a year as well as 2 billion pieces of third-class mail.

A continued loss of parcel post volume to such private firms as United Parcel Service would lead to higher costs - and higher rates - for other postal customers who would have to absorb more overhead costs, the agency stated yesterday.

TR for PICKUP . . .

Specifically the postal board proposed:

Restructuring rates for existing parcel post bulk mailings. For example, a 5-pound parcel being sent 1,000 miles would cost $1.86 compared with $2.14 today. In order to qualify, customers would be required to deposit 50 or more parcels in containers acceptable to the Postal Service.

Establishing a new class of third-class mail presorted to carrier routes with a minimum per piece rate of 6.9 cents, or 1.5 cents lower than the current rate of 8.4 cents for regular bulk third class. Bulk mailers would have to send at least 2,000 pieces per mailing with at least 10 pieces per carrier route, to qualify.

Inaugurating a service called electronic computer originated mail, allowing customers with computer capability and sufficient volume to transmit messages electronically to 25 specially equipped post offices. Upon delivery, these messages would be printed electronically, mechanically sealed in envelopes and processed for normal mail delivery.

The new electronic messages would be delivered within two days anywhere in the U.S. and would cost between 30 cents and 55 cents a message, depending on volume. The joint Western Union-Postal Service Mailgram offers one-day service but is more expensive.

The Postal Service said the new service could begin as early as Dec. 15 and that 750 companies now have sufficient mail volume and computer capability to take advantage of the electronic delivery service.