Windows2003 is not installed by default, we must add it manually. The POP3 service component, under Add/Remove Windows Components-e-mail services, includes two items: POP3 Service and POP3 Service Web management;
Click "Start-management tools-POP3 Services", open the POP3 Service Main window, then click the host name (native) under POP3 service on the left side of the window, and then select "New Domain" on the right side, and enter the name of the mail server that you want to create in the "Add Domain" dialog box, which is the section behind the @ sure you can.
Then create the mailbox. On the left click on the domain name just built, select "New Mailbox", in the pop-up dialog box to enter the name of the mailbox (that is, the previous part of the @), and set the mailbox password, the final set as shown in Figure 1.