i have a domain called college edu.org as a public registered domain and i am having an exchange in my infrastructure. firstname.lastname@example.org and created an mx record poining to my exchange server
i need to create a new domain name for my students to use the mail address. So i have decided to create a subdomain in my external dns called student.colleg.edu.org, so that my student mail id will like email@example.com. and need to point an mx record to microsoft windows live server , exchange labs
now when a user send a mail from outside to my student mails, it gives an NDR , unknown host firstname.lastname@example.org.
i think this is an error with DNS, could anyone help me to setup up the subdomain in my external dns