(a) Service of a complaint or notice of hearing shall be made by certified or registered mail or by delivery in any manner authorized by Rule 4(d) of the Federal Rules of Civil Procedure.
(b) Proof of service, stating the name and address of the person on whom the notice was served, and the manner and date of service, shall be made by:
(1) Affidavit of the individual making service;
(2) An acknowledged United States Postal Service return receipt card; or
(3) Written acknowledgment by the respondent or his representative.