To create an alias that anyone can use, you must have root access to your system. Edit your /etc/aliases file using any text editor. Under the Local Aliases category, on a separate line, type aliasname:username,username. Separate each item with a comma and end the group with a Return. You can include a space after each comma, if desired.
Figure 4-42 shows an example of an alias group in /etc/aliases.
To use the alias, type the name of the alias in the To, Cc, or Bcc line of the Compose Messages window. The names you typed in the field are not expanded as part of the outgoing message. The alias group itself is displayed as the user name when the message is received. To use an alias on someone else's system, type the alias name, @, and their machine name in the To, Cc, or Bcc line of the Compose Messages window. For example, someone else could send mail to the "friends" alias in the example by typing friends@castle, because the "friends" alias is on the machine "castle".