Mo. R. Sm. Clm. Div. Cir. Ct. 142.02
Service may be made by methods for obtaining service of process in circuit courts or by mailing a copy of both the summons and the petition to the defendant at his last known address by certified mail, return receipt requested, delivery restricted to the addressee. If service by mail is attempted, the envelope and the return receipt shall be stamped with the docket number of the case. The receipt for certified mail shall state the name and address of the addressee and the date of mailing and shall be attached to the original summons. The return receipt when signed by the addressee or, if the addressee is a corporation, its agent, and when returned to the clerk of the small claims division, shall be attached to the original summons. If the return receipt shows delivery at least ten days before the day for appearance, it shall constitute proof of service.
Mo. R. Sm. Clm. Div. Cir. Ct. 142.02