jluerken,
Hivemail does not use individual postboxes hence it does not offer pop3/imap support. There is only one mailbox (a catchall account) and it is checked either via a scheduled script (windows) or via a cron job (linux).
If you want to create a user you just enter their details (as per my post) in the database and if you want to delete a user you just delete that entry from the relevant table.