Okla. Stat. tit. 58, § 58-707.1: Persons who may serve - Proof of service

Whenever personal service of a notice or citation is prescribed

in any section of the probate code, service shall be made by any

person not personally interested therein unless service of the

notice by a sheriff is ordered by the court. Proof of such service

by a person other than the sheriff shall be made by affidavit of the

person making the service.