The Collaborative International Dictionary of English v.0.48:

mail carrier \mail carrier\ n.
   A person who delivers the mail; -- also called a letter
   carrier. A male mail carrier is also called a mailman.

   Syn: postman, letter carrier, carrier, mailman.
        [WordNet 1.5 +PJC]

The Collaborative International Dictionary of English v.0.48:

mailman \mail"man`\ n.
   A man who delivers the mail. A male mail carrier.

   Syn: postman, mail carrier, letter carrier, carrier.
        [WordNet 1.5] mail-order buying

WordNet (r) 3.0 (2006):

mailman
    n 1: a man who delivers the mail [syn: mailman, postman,
         mail carrier, letter carrier, carrier]