Mich. Comp. Laws § 700.1009

Sec. 9. To the extent a power of attorney grants an agent authority over the content of electronic communications sent or received by the principal and unless directed otherwise by the principal or the court, a digital custodian shall disclose to the agent the content of electronic communication if the agent gives the digital custodian all of the following: (a) A written request for disclosure in physical or electronic form. (b) An original or copy of the power of attorney granting the agent the authority over the content of electronic communications of the principal. (c) An affidavit from the agent under section 5505 of the estates and protected individuals code, 1998 PA 386, MCL 700.5505. (d) If requested by the digital custodian, any of the following: (i) A number, username, address, or other unique subscriber or account identifier assigned by the digital custodian to identify the principal's account. (ii) Evidence linking the account to the principal.