I can exchange mails with local usrs. My mail server's IP is 10.14.213.15. But when I exchange mails with remote hosts, all of the remote hosts in different network sections can receive my mails, but I can not receive any mails from those host except the host (10.14.208.77),which is one hop from me. My DNS(10.14.213.15) is transfer by that host(10.14.208.77.) What is the problem ? Do you think the problem focus on DNS of that host?