Why isn't the server's domain passed to Asterisk when I receive an incoming call from another server?

Question

Asterisk

Here is the situation: I set up asterisk along with freepbx for sip2sip calls. They seem to work, but when there is a call from another server to my server, Asterisk replaces the domain name with its own. Thus, if [email protected] calls, the receiving subscriber displays [email protected] domain of my server. How can this be fixed?