Michigan Compiled Laws, Chapter 600. Revised Judicature Act of 1961 § 600.1930

Sec. 1930. Service of process upon any defendant may be made by leaving a summons and a copy of the complaint with an agent authorized by written appointment or by law to receive service of process. Whenever, pursuant to statute, service of process is to be made on a nongovernmental defendant by service on a public officer, the service on the public officer may be made by registered mail addressed to his office.