Hi 2all, there is one network with postfix as mail server. The usernames and passwords are simple because it is a school network. We have set a classroom in another house up, that is 10 km away. On the postfix exist all clients of that room and they can receive and send the post. But only to internal clients. How can we allow the clients not only to receive the external post, but also to send answers to the internet? For example: The client in the postfix-network has an address aXY@???.com (XY – the numbers) The client in the second network has an address bXY@???.com A mail sent from email@example.com to both clients can be received, but only aXY@???.com can answer this mail, because of local relay only. How can we allow the relay from the second network also? Postfix network has a static ip, the second network has a dynamic ip.