The Users tab in the VPOP3 settings lets you manage the list of Users handled by VPOP3.
At the top of the page (1) is a count of the number of messages defined, and your licence limit (if your licence is unlimited, then the limit is not displayed).
Below that (2) are some buttons to perform actions which aren't specific to a single user:
Under those buttons is a count of the messages waiting to be sent out (3), and a table showing all the Users defined in VPOP3 (4).
You can view & delete messages waiting to be sent out by clicking on any of the text in the Outgoing Message Queue line.
You can edit a user by double-clicking on the user entry in the list. You can edit several users at once, which can make it easier to compare the settings of a couple of users.
You can delete a user by selecting the user entry in the list, and pressing the Delete button (6).
Note that it is currently not possible to rename a user. In most cases this is unnecessary as you can use Aliases to give a user different email addresses.