Mich. Comp. Laws § 450.1243: Resignation of resident agent.

Sec. 243.

A resident agent of a domestic or foreign corporation may resign by filing a written notice of resignation with the president or a vice president of the corporation and with the administrator. The corporation shall promptly appoint a successor resident agent. The appointment of the resigning agent terminates upon appointment of a successor or upon expiration of 30 days after receipt of the notice by the administrator, whichever first occurs. Upon the resignation becoming effective, the business or residence address of the resigned agent shall no longer be the registered office of the corporation.