I have just installed POSTFIX on a Debian box, I pointed the relay host config setting to an exchange server which will deliver the mail to external users.

So what I am trying to do is telnet to the debian box and send an email to [email protected] which will then be past to the exchange server for delivery.

The problem is I get the following:

rcpt to:[email protected]
554 relay access denied

I have seen a section in the config "mydestination" but i want the exchange server to decide which domains it will deliver for and not the POSTFIX server.