39 C.F.R. § 491.2
Service of process on the Authorized Agent or his designee may be made in person or by certified or registered mail, with return receipt requested, at the address of the Authorized Agent. Service may also be made on the Authorized Agent by means of any private delivery service pursuant to its authority for the private carriage of letters under an exception to the Private Express Statutes, 39 U.S.C. 601 - 606 , provided that the private delivery organization issues a receipt bearing the name and address of both the addressee and sender, as well as the date of delivery and the signature of the receiving agent. No garnishment is effectively served until it is received by the Authorized Agent or his designee regardless of the chosen mode of delivery. Process addressed to, delivered to, or in any manner given to any employee, other than the Authorized Agent or his designee, may, at the sole discretion of the employee, be returned to the issuing court marked "Not Effectively Served." A copy of or reference to these regulations may be included. Employees are not authorized to redirect or forward garnishment process to the Authorized Agent. In the event that the address of the Authorized Agent is changed, mail may be forwarded from his last published address to his new official address until such time as these regulations are amended to reflect the new address.
39 C.F.R. § 491.2