Mo. Rev. Stat. § 375.256
Any insurance company, association, or other insurer not incorporated or authorized under the laws of this state, which shall do or cause to be done any of the following acts in this state, effected by mail or otherwise: the issuance or delivery of contracts of insurance to residents of this state or to corporations authorized to do business in this state, the solicitation of applications for contracts of insurance, the collection of premiums, membership fees, assessments or other considerations for contracts, or any other transaction of business, shall be deemed to have constituted and appointed the director of the department of commerce and insurance of the state of Missouri, and his successor or successors in office, to be its true and lawful attorney, upon whom may be served all lawful process in any action, suit, or proceeding instituted in any county in this state, by or on behalf of an insured or beneficiary arising out of any contract of insurance, and any such act shall be signification of its agreement that the service of process is of the same legal force and validity as personal service of process in this state upon the insurer, notwithstanding the fact that the insurance company, association, or other insurer has failed or neglected to file written power of attorney appointing and authorizing the director of the department of commerce and insurance of this state to acknowledge or receive service of all lawful process for and on behalf of the insurance company, association or other insurer, as provided in section 375.906.
§ 375.256, RSMo