I have a mailserver M answering port 587 but only for a given authorized machine A. From my regular machine R, I want to contact M on 587 via A. I have full control over A and R, but but M.
Can I setup SSH tunnels and port forwarding for that?
I've read several posts describing SSH port forwarding, but it seems the usual examples don't discuss such a use case. E.g., this link discusses Local Port Forwarding and Remote Port Forwarding, but neither would seem to do the trick in this situation.
I can setup e.g. Local Port Forwarding such that port 587 on R in redirected to some port on A, say 5877, but how would I setup A such that incoming traffic on port 5877 is redirected to port 587 on M?
