Service of any document in a pending administrative proceeding may be accomplished by personal delivery or by mailing such document addressed to the party or the party's authorized representative at the last known address, postage prepaid. In the alternative, upon written consent of the party filed in the administrative proceeding, service of any document may be made by electronic mail to the address provided by the party or the party's authorized representative. The document shall indicate on its face by Certificate of Service or Mailing that copies have been served on parties of record.
Okla. Admin. Code § 710:1-5-45