I am still having the looping error when sending from 2003 account to the cloud through the Exchange 2010 server. I tried already two solutions:
-Unchecked the box “ This Exchange Organization is responsible for all mail delivery to this address according to this below:
( didn’t work)
-Suppress Link State Updates (didn’t work)
Here is the issue description and error: Looping issue between 2003 and 2010
The issue is related to the Exchange 2003 server NDR error 5.4.6. It is also logged in the Event Viewer with the event ID: 3020 below: “A non-delivery report with a status code of 5.4.6 was generated for recipient x-ex;/O= INTERNATIONAL/OU=External (FYDIBOHF25SP)/cn=Recipien
f37f9e1d (Message-ID <481B48D1DD85704BBC76A10F8
Cause: A forward loop was detected by the categorizer. This is a common hosting configuration problem caused when someone uses the provisioning tool to create a contact in one organization unit and creates a user in a different organization user that share the same e-mail address.
Solution: Verify that you do not have a user in organizational unit and a contact in a different organizational unit that have the same e-mail address”.
Your message did not reach some or all of the intended recipients.
The following recipient(s) cannot be reached:
A configuration error in the e-mail system caused the message to bounce between two servers or to be forwarded between two recipients. Contact your administrator.
Here is little more on the issue:
Mail flow is working all around otherwise from 2k3 to 2010 and back and from 2010 to the cloud and cloud to 2010 Hybrid. I only get this error when trying to send from 2k3 account to the cloud user which has the same domain since this is a Hybrid scenario (coexistence). So, when the 2003 user@domainA.com sends to the user2@domainA.com (which is cloud mailbox) it needs to go through the Hybrid server and it throws back the error mentioned above. From 2010 to cloud no issues.