Mo. Rev. Stat. § 32.042: Director of revenue may be served, how — proof of service.

Service of a summons and petition upon the director of the department of revenue may be made in the manner provided by subsections 4 and 5 of section 506.150, provided that in lieu of the acknowledgment provided by said section, service may be made by certified mail, return receipt requested, and such receipt when returned indicating delivery of such mail shall serve as proof of service.