VPOP3 contains a list of 'Users'. Each User has an associated 'Mailbox'. The 'Mailbox' is where messages for that person are stored. One or more users can be designated as 'Administrators'. Administrators are allowed to configure VPOP3.
By default, each user has a single Internet email address of mailboxname@company.co.uk. However, by defining mappings you can make a user have multiple Internet email addresses, or make a single Internet email address correspond to multiple users.
When you first install VPOP3, it is set up with a single user who is an administrator An Administrator is a VPOP3 user who is allowed to change VPOP3 settings, add/remove users, view queued messages etc.. The user name and password of this initial user are entered by the user during initial installation (not during an upgrade or reinstallation) - the default username is 'Postmaster' and the default password is 'admin', but these can easily be changed during installation.
To configure VPOP3 you need to get into the VPOP3 settings. Usually you will do this by right-clicking on the red post-box in the Windows taskbar. A menu should appear, and you choose 'Settings'. Your web browser should appear with a login screen. Enter an administrator's login details, then go to the Users page.
(More details on entering the VPOP3 settings are available here)
The little 
symbol next to Postmaster
indicates that this user is an administrator. There are several other
symbols which can be shown (as well as combinations), for more details
see the information on the User
Accounts page
To add a new user, you press the 'New' button which will take you to the Add User Wizard
For more details on the Users page, see the help on the User Accounts page
