Może tak:
XYZ will accept bid offers for a contract to supply ABC. All interested parties are requested to mail their offers to the address submitted below by DD.MM.YY. The envelopes shall be opened on dd.mm.yy. The result of the bid contest shall be made known to each of the participants by mail. My [Our?] best regards, x
Jeśli to jest jakieś publiczne ogłoszenie, to "z poważaniem" wydaje się wydatnie zbędne, IMO.