An Admin user may designate a user account to receive blind carbon copies (Bcc) of mail sent to the system or to unknown local users. Though any account on the system can be designated to receive this mail, the traditional UNIX user is the "postmaster" user. If you would like to set up a postmaster account on your system, create a user with a long name of "postmaster" and a short name of "postmstr". The latter accommodates the eight-character short name limit present in server versions 10.0.3 to 10.1.4. Mac OS X Server 10.2 and later allow the "short name" to be as long or longer than the "long name," up to 255 characters.
Alternately you may create an account of your own choosing and use it as you would the postmaster account.