Fixing FreeBSD Qmail Server

Please note that, it is not a common Linux , its a freeBSD so please don't waste time of both you and us by bidding on it without proper knowledge. Normal Linux commands do not work here. We have a freeBSD qmail server, we use it as a mail server, the issue we have faced is, it is not sending emails to outside world except virtual domains hosted in the server. The server worked perfectly until the issue occurred. When we further investigated the issue we find that some email forging is going on where someone is sending emails from a domain using our server. So we need the following fixed ASAP 1. Get the email working 2. Secure the server from this kind of attacks.