A mailman is the person who brings letters and parcels to your house. It is the usual word in American English. In Britain people more often say postman. Though actually, the job was never only for men, and many of the people who do it today are women; careful American English now likes mail carrier or letter carrier, which does not pick a sex. Families still say mailman without thinking, the way they once said milkman even when the person had changed. It is everyday speech, a little old-fashioned in careful writing, but nobody will look at you strangely for it.

郵差（口語）。台灣郵局正式職稱是「郵務士」；中國大陸較常說「郵遞員」。