VPOP3 Enterprise supports IMAP4 email clients (VPOP3 Basic does not).
With IMAP4 the email folders and messages are stored on the mail server. The email client then synchronises with the server. Also, unlike with POP3, several things can access the same mailbox at once.
This means that several people can access the same mailbox, and you can also access the mailbox from several places (eg from an office PC, a home PC, a laptop and a mobile phone), and all computers will be able to see the same folders and messages - if you read, delete or move a message in one place, that change is copied to all connected devices. Also, if you send a message from one device, that will be visible in the 'sent items' folder on all devices.
To use IMAP with VPOP3 Enterprise, you do not have to do anything in VPOP3 at all. Simply create a new account in your email client (or device) and, for the account type choose IMAP4 (or 'IMAP'). The standard 'port' used for IMAP4 is port 143.