I am not sure if is the right place I just started a new job and the person before setup exchange. The end-users can send and receieve from each other inside the company , and can send outside the company but they cant receieve from outside the company. Can you help point me in the right direction

Check recipient policy in System Manager. Make sure that is correct so that external users will know how to reply. Also, make sure that your MX record is properly pointing to your external ip address. Let me know how you make out.