All Emails from a Domain into a Inbox?

Hi I dont know what my Hoster used before but I had an E-Mail Adress where all the Mails to the Domain where delivered. Like -> tjattaejte@domain.at, dtjsdtjskzsrzksr@domain.at,... all are in my Inbox with the right Adress not like a normal forward where your E-Mail Adress is used. It was intend for an (Microsoft) Server to use pop3 to download all Mails and Distribute them internally. After the Import my Inbox is still configured to that feature but I dont find any setting to configure it?! What I would like is something like that: a) The Mail Adress have an Account in Cpanel -> forward the E-Mail to the Account/ if not than b b) The Mail Adress dont exist on the Server -> forward the E-Mail to the "all in" Mailbox Thanks