mmoamen You need to configure your NS (Name servers) to point to your server IP.
Example:
A Record @ points to 123.456.789
as 123.456.789 is your machine IP.
A Record @ points to mail.domain.com
as 123.456.789 is your machine IP.
You need to understand how your DNS configurations work to be able to point your emails and other configurations into your machine (server).
If you cannot do it, I can set them up for you. Let me know.