Mo. Rev. Stat. § 409.541: Secretary of state deemed offeror's agent, when — service of process, how, effective when.

1. Every nonresident offeror, whether or not such offeror has filed a registration statement, except a foreign corporation which has appointed and keeps a resident agent in this state, shall be deemed to have appointed the secretary of state as his agent upon whom may be served any lawful process, authorized by sections 409.500 to 409.566, with the same effect as though served upon the offeror personally.

2. Service of process pursuant to this section shall be accomplished by leaving a copy of the process in the office of the secretary of state, but it shall not be effective unless notice of the service and a copy of the process is sent by certified or registered mail to the nonresident offeror served, at his last known address.