[regiemon]

i am currently studying postfix and i am really having a hard time.
would like to know if we live run our mail server how does the example.com will be pointed to our server.
for example. someone sent me an email using yahoomail to regiemon@example.com
how does yahoo.com would know it will be delivered to our mail server?
sorry for the dumb question.

thanks.

[Law]

Your domain would have to be register first, than the yahoo user (his DNS) would find you through the root hint. If you register in the .com, then you would be under .com some where. That's just the basic, it's actually more complicating than that, a great book to read is "DNS and BIND 5th Edition".