registered post
noun [ U ] UK uk/ˌredʒ.ɪ.stəd ˈpəʊst/ us/ˌredʒ.ɪ.stɚd ˈpoʊst/ (US registered mail)
挂号邮寄
a way of sending letters or parcels by using a service that deals with them in a special way and makes sure they do not get lost
You'd better send the cheque (by) registered post. 这张支票你最好挂号邮寄。