it will be a very nice feature, that its possible to set the allowed addresses for pop3/smtp proxy. so that i can add all internal used adresse to a allow list, or that de ASG box use the active directory to read the users mail adresses. so its not possible, that mails wich have a reciver address wich doesnt exist, will come in or that someone wich have no allowed mail adress can get mails.
eg. if you have have a client wich just can download messages via pop3 wich are send on mailaddy@domainone.com and not the mail on laggybaggy@freetime.net or so...