MonitorWare Knowledge Base

I am running a server on Windows Server 2003 with Microsoft Exchange, and I'm a newbie. Basically, the situation is is that one of our business' email accounts is a Universal Distribution Group with two users set as members. The first user is receiving all the group emails while the second is not. I took off all the users on the group list and put them back on; when I sent a test email, they both received it, but when other emails were sent from other people, only user #1 received them. My theory is is that the group is only sending emails to user #2 that are from our local domain. Can anyone help me with this?