Washington Motion to Serve by Mail is a legal procedure in which a party in a civil case can request to have documents served to another party through the mail instead of in-person. This procedure, also known as "service by publication," is regulated by civil rules of procedure in Washington state. There are two types of Washington Motion to Serve by Mail: service by certified mail and service by regular mail. Service by certified mail requires the sender to provide a return receipt to the court to verify delivery to the recipient. Service by regular mail does not require a return receipt and is generally used when the identity of the recipient is unknown.