(1) After service of a contested case notice, all subsequent notices including amendments to a contested case notice, motions, briefs and other papers pertaining to a pending administrative action must be served on all parties. Service may be made by regular U.S. mail, postage prepaid, addressed to each party at:
(a) the mailing address provided by the party in the request for hearing or a subsequent mailing address provided by the party;
(b) the party's last known mailing address if no request for hearing was made, or if the request for hearing failed to include an address; or
(c) the address of the place where service of the original contested case notice was achieved, if the party's mailing address is not known to the CSSD.
(2) Proof of service must be attached to each document as provided by ARM 37.62.911.
(3) When the requirements of this rule are met, service by mail is complete upon mailing.
(4) Service on the CSSD does not constitute a filing with the OALJ and filing with the OALJ does not constitute service on the CSSD.