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We have two exchange 2007 servers. One is a Microsoft Exchange Edge Transport server in the DMZ the other one is also a MS exchange server installed in the internal network. The firewall is configured to allow ALL ports and protocols from Internal to DMZ and TCP Port 25 from the DMZ situated Edge Transport to the internal mail server.

Everything was working fine, but all the sudden this morning outlook client stopped receiving emails from the Internet. Mails are queuing up in the Edge Transport Server (not able to deliver to the internal mail server). Verified that there were no firewall changes and telnet to port 25 on both email servers were working. But, unfortunately the mails are not being sync'ed from the Edge Transport to Internal Mail server.

Sending email from Outlook client to the Internet do work though.

Due to single mail server, I am urgent asking help from the community. Your assistance are high appreciated.



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Hi guys I found the problem and fixed it. The SMTP log has error "Insufficient resources". After googleing and troubleshooting, found that the culprit was the disks space that hosts the "Transport Queue Database" and the "Transport Queue" I edited the file C:\program files\microsoft\exchange server\bin\edgetransport.exe.conf" to point the transport queue and transport queue log to D:\ drive where we have a lot of space. The mails are flowing again. Thanks to all for your help. – Eric Feb 8 '10 at 7:29

Check that all internal DNS records are as they should be. Especially the internal DNS records for the hub transport. Then delete the Edge Subscription from the edge server and the active directory site and recreate it.

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Thanks Wesley. Verified that DNS records for the hub transport is correct. – Eric Feb 8 '10 at 7:23

There is a command you can run in the Console that may give you more information:


Another thought: Have you applied any updates to your servers? For instance, did either your Hub Transport or your Edge Server get updated to Exchange 2007 SP2, leaving the other one behind? You'll want to make sure BOTH servers are up to date on the latest packages.

Lastly, Wesley's advice is sound. Deleting and recreating the subscription is painless and worth-a-try.

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We are running SP1 on all servers. Upgrading to SP2 is a good idea though not sure what benefit it will bring. – Eric Feb 8 '10 at 7:25
You don't have to update. I'm asking you if one or the other recently applied an Exchange update. If so, you'll want to make sure that both servers are the same. Otherwise, no need. – tcv Feb 8 '10 at 12:29

Here are the ports that need to be open on firewall for Edge Server to work properly:

For Inbound traffic: SMTP - TCP port 25 (from Internet) SMTP - TCP port 25 (from Edge server to Hub server on internal network) For Outbound traffic: SMTP - TCP/UDP port 25 (from Edge to Internet) SMTP - TCP/UDP port 25 (from Hub to Edge server) LDAP for EdgeSync - TCP port 50389 (from Hub to Edge server) Secure LDAP for EdgeSync - TCP port 50636 (from Hub to Edge server)

Since Edge server needs to communicate with Hub server it is important that it can resolve Hub transport servers by FQDN and Hub transport servers must be able to resolve Edge servers by its FQDNs.

To accomplish this you need to either open 53 (DNS) port and configure internal network adapter to use internal DNS but as a security precaution I would suggest to enter DNS records for Edge servers on local DNS manually and to fill hosts file on Edge servers with FQDNs for Hub transport servers.

I would first test that the edge server can resolve the hub server's FQDN. If it can't then yuo know you have a DNS problem (at least) after resolving that , or if there is no DNS problem delete the Edge Subscription from the edge server and the active directory site and recreate it.

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Thanks Jim B. I did verify that that the communication scheme you described is configured and working. – Eric Feb 8 '10 at 7:24

You might check to see if the certificate on your edge server is expired. Do a Get-ExchangeCertificate | fl. If it is expired you'll need to generate a new certificate and delete/recreate the edge subscription.

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