I have a problem configuring an Exchange server, is a simple installation, the LAN is the Exchange server: serverxch.central.abc.es, belonging to the domain (abc.es). I have a firewall to create a DMZ, and this, I created a perimeter server, called: mailserver, outside the domain I created the subscripccion and I imported from the server "serverxch.central.abc.es. From the server on the LAN can access the edge server port 25, and from edge to hub. From the Lan I send a mail out and I work but if I throw an email from the DMZ to an internal account is not able to reach the server with the mailboxes, I get DNS error. I still have the server a test phase until you correct this problem. I have installed a DNS server on the perimeter to tell the server IP on the LAN, but the messages still remain in line at the edge server with DNS failure. (DnsConnectorDelivery - "451 4.4.0 DNS Query Failed") domain name internally and externally is the same, I'm afraid I may have something to do with it. Since I find that if I nslookup resolves the server IP "serverxch.central.abc.es" Has anyone had any similar problem? Internal and External name of Domain (abc.es) SERVER MX Current - 213.195.XX.XX NAT to server DMZ(192.168.2.1), until it is in production. ---------------- LAN ------------------- serverxch.central.abc.es (192.168.0.34) - Exchange Server - Domain Controller - DNS Server ------------- Firewall ----------------- LAN, DMZ, WAN Open ports from DMZ to LAN: TCP - 25, 389, 50389, 50636 UDP - 50636 DNS ??? Open ports from LAN to DMZ: TCP - 25, 389, 50389, 50636 UDP - 50636 DNS ??? ---------------- DMZ ------------------- name server: mailserver, out of domain in Workgorup (192.168.2.2) - Edge Server of Exchange - DNS Server

Hello,can you resolve your MX records using your dns? Issue might be your DNS server setup. Is the DNS on the edge and LAN primary?Isaac Oben MCITP:EA, MCSE

Please refer to the similar thread to troubleshoot:Queue Problems - 451 4.4.0 DNS Querry Errorhttp://social.technet.microsoft.com/Forums/en-US/exchangesvrtransport/thread/440dbf97-9c8e-4ced-81f3-565b4869ef59Regards,Xiu