I use Exchange server 5.5 for my email server. I have created email@example.com and it's already been worked out and done. Now I want to create the firstname.lastname@example.org I have tried to configure and setted up in the DNS Manager NT using A and MX record. and also set to inbound in the Internet Mail Service. But it's still won't work at all. I mean I can sent using the email@example.com but when I tried using my hotmail sent to firstname.lastname@example.org, it's look like never succeeded. it resulted as a Unknown Host. Why is this happen?? is it means that there's something wrong with the DNS? What should I try to configure in the Exchange?