Okla. Stat. tit. 5A , app 1-A § 13.1
Service of any and all correspondence, notices, and any formal complaint, in connection with proceedings under these Rules, whether before or after the filing of a formal complaint, may be made upon the respondent lawyer or applicant for reinstatement in person or by mail directed to the respondent or applicant at the last address shown on the official roster of the Oklahoma Bar Association, unless and until the respondent or applicant, or counsel for the respondent or applicant, shall cause to be delivered to the General Counsel a notice reflecting a different address. Oklahoma Bar Association members are required to provide a current address to the Association and to inform the Association of any changes in address in accordance with the requirements of the Rules Creating and Controlling the Oklahoma Bar Association. Proof of mailing to the respondent or applicant at such address shall be sufficient to prove service. Except as otherwise specifically provided in these Rules, service may be made by regular mail.
Okla. Stat. tit. 5A , app 1-A § 13.1