Mo. Rev. Stat. § 287.520: Notice — manner of serving.

1. Any notice required under this chapter shall be deemed to have been properly given and served when sent by registered or certified mail properly stamped and addressed to the person or entity to whom given, at the last known address in time to reach the person or entity in due time to act thereon, or to counsel for that person or entity in like manner. Notice may also be given and served in like manner as summons in civil actions.

2. Notwithstanding the provisions of subsection 1 of this section, the division may serve or send any notices required under this chapter by electronic means, except that any notices required to be sent to an employee not represented by counsel shall be sent by registered or certified mail to the last known address of the employee unless the employee consents to receive notices by electronic means. In the event the employee is represented by counsel and counsel is sent proper notice under this chapter, notice to the employee may be sent by regular mail.