Mich. Comp. Laws § 750.390

Sec. 390. Malicious annoyance by writing—Any person who shall knowingly send or deliver or shall make, and for the purpose of being delivered or sent, shall part with the possession of any letter, postal card or writing containing any obscene language with or without a name subscribed thereto, or signed with a fictitious name, or with any letter, mark or other designation, with the intent thereby to cause annoyance to any person, or with a view or intent to extort or gain any money or property of any description belonging to another, shall be guilty of a misdemeanor.