Exchange 2013 - Some messages net being delivered with shared SMTP Address Space

Question

Hi
I am having a problem with some internal messages intermittently not being delivered. When I go to the Exchange ECP -->Mail Flow -->Delivery Reports I can see the following error with the message:
Submitted
2013-03-07 11:36 AM EXCHANGE
The message was submitted to exchange.******.local.
Pending
2013-03-07 11:36 AM exchange.******.local
Message was received by exchange.******.local from Exchange.******.local.
Failed
2013-03-07 11:36 AM exchange.********.local
The domain name in the email address is incorrect. Check the address.
554 5.4.4 SMTPSEND.DNS.NonExistentDomain; nonexistent domain
However, usually just waiting a few minutes and then sending to the same recipient, the message will be delivered:
Submitted
2013-03-07 11:41 AM EXCHANGE
The message was submitted to exchange.******.local.
Pending
2013-03-07 11:41 AM exchange.******.local
Message was received by exchange.******.local from Exchange.******.local.
2013-03-07 11:41 AM exchange.******.local
The message has been transferred from exchange.******.local to Exchange.******.local.
Delivered
2013-03-07 11:41 AM exchange.******.local
The message was successfully delivered.
I have setup an Accepted Domain as Internal Relay, with a Send Connector to deliver any mails if the user is not found in Exchange server.

Answer 1

Hi All
I had this issue as well.
Here is the solution i used to fix this once for all:
My Environment:
AD server with private and public NICs
Exchange Server with Private and Public NICs
Used a dummy domain (Not owned by me) (ex: corp.com) on Private Network.
Created accepted domains for the domains that i own on exchange server.
Issue Cause:
When an external user (Gmail, hotmail.. etc) sends an email to my accepted domain, as the MX record is pointed to my exchange server on the public IP, the mail flows till my exchange server. Now the transport service on the CAS, hand's over the email to
Transport Service on the Mail box server. There it goes to the categorizer. Here the DNS look up happens and the next SMTP send service will either hand over the mail to the Mail box or send a Non delivery report stating that a mail box, domain name is not
found with in itself. 
The issue here is caused by our private DNS where it fails to resolve the internal dummy domain that i used because the resources on the DNS server was completely utilized my memory ballooning in VMware. Ignore the ballooning thing if you do not understand.
Resolution:
I created an entry in the C:\Windows\System32\Drivers\etc\hosts file of the exchange server as below:
mail01.corp.com 192.168.80.132 .i.e., <host name of the exchange server>.<domain prefix>.<domain suffix> <Private IP address of the exchange server>
I change the secondary DNS on the Private NIC of the exchange server to itself .i.e., 192.168.80.132 and forced it look within itself when the primary DNS does not respond at times.
Now my exchange server is absolutely stable. It worked for me ! 
Hope this post helps you fix the issue or at least help you think a bit ahead.
To understand more about your scenario, i would suggest you look up the logs at C:\Program Files\Microsoft\Exchange Server\V15\TransportRoles\Logs (if you have not changed the default drectory while instalation) and Frontend Connectivity logs and Mailbox
connectivity logs. I am sure those logs will help you understand whats going wrong behind the scenes.