We are hosting a domain's email on a server we have that's on it's own WAN address. We also host our companies website on it as well, while our email is on another server with it's own WAN address. They are on different subnets as well. They can send and receive emails from everyone, but they can't send one to us. We can send and receive emails to/from everyone without a problem. I know it's a DNS issue but I don't know where to begin to look. Any help is appreciated. Thanks.