I have a setup like below.
My domain xxxx.com is hosted in ISP with arround 50 users. I am downloading arround 40 users mails to my exchange 2007 using 3rd party smtp software. Now I am facing issue when sending e-mails from exchange to that 10 users (their ID's are not created in exchange). The exchange will bounce back with No such user error. So Now I want to configure exchange to send all other users mails (10 users) using DNS. How I can configure in exchange. (In mdaemon I have a option called, unknown user mail forward)