Okla. Stat. tit. 5A , app 7 R. 16
Every order required by its terms to be served by the Clerk or required by these rules to be served by the Clerk, or every pleading subsequent to the original petition and every written motion shall be served on the party or parties affected thereby.
Attorneys filing motions, demurrers or other pleadings subsequent to the original petition shall deliver or mail copies thereof to the party affected thereby or to his counsel of record, on the same day of filing, and a statement as to such delivery or mailing shall be noted by the attorney on the original instrument filed.
The Clerk shall deliver or mail a copy or copies of any order required to be served, to the party or parties affected thereby or to his or their attorney or attorneys of record on the same day of the entry of said order, and a statement as to such delivery or mailing shall be noted by the Clerk on the original order filed.
Service upon the attorney or upon a party shall be made by delivering a copy to him, or by mailing it to him at his last known address. Service by mail is complete upon mailing.
Okla. Stat. tit. 5A , app 7 R. 16