Mont. Code Ann. § 32-2-1215

Any service required or authorized to be made by the department pursuant to this part must be made on individual board members and officers by personal service and may be made on institutions by registered or certified mail or common courier with tracking capability or in any manner reasonably calculated to give actual notice as the department by rule or otherwise may provide. Copies of any notice or order served by the commissioner pursuant to the provisions of this part on any institution or any board member, officer, or other person participating in the conduct of the institution's affairs may also be sent to the appropriate federal supervisory authorities.