Mont. Code Ann. § 33-1-604
Service of process -- domestic insurer
33-1-604 . Service of process -- domestic insurer. (1) Service of process against a domestic insurer must be made pursuant to 35-7-113 or in any other manner permitted by law.
(2) Service of process against a domestic reciprocal insurer must be on the attorney-in-fact or in any other manner permitted by law.