Mo. Rev. Stat. § 141.460

Affidavits of publication of notice of foreclosure, and of posting, mailing, or other acts required by sections 141.210 to 141.810 shall be filed in the office of the circuit clerk prior to the trial, and when so filed shall constitute part of the evidentiary documents in the foreclosure suit. Such affidavits shall be prima facie evidence of the performance of the acts therein described, and may be so used in the trial of the suit, unless challenged by verified answer duly filed in the suit.