[otrs] How to allow email tickets from a group only

Hi, I have several queues with different groups having write access to it. In the Web user interface only those groups can create tickets in these queues as expected. However, sending a ticket via email and filtering that into one of these queues have no group control. How can I control the group of the sender (email->group) and reject the ticket if that customer is not in the group of the queue? Regards, Bulent Oktem