All email going to Poison Queue in Exchange 2106

I set up a new domain and a new Exchange 2016 server and noticed that no email is being delivered to any mailboxes. Whether from one user to the other on the exchange server, or whether external email is being sent in, all email is going to the Poison Queue. Why, and how can I stop this behavior?

Some steps I have taken:
- tested the domain at (comes up clean)
- tested the domain at and all tests come up clean
- tested from iPhone too, same result. Messages show up in "Sent" but nothing is being delivered.
- enabled logging on the send and receive connectors, then examined the logs. I see no errors.
AaronSSHIT ConsultantAsked:
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AaronSSHIT ConsultantAuthor Commented:
I followed the steps in this article and it resolved the mail flow issue!
Jose Gabriel Ortega CEE Solution Guide - CEO Faru Bonon ITCommented:
Let's start with the basic.
Are you sending emails within the same local domain in the exchange 2016?.
Do you have a send connector?

did you configure SPF, virtual folder's URLs, and the public certificate?

do you see any errors in the Event log for the exchange server?
AaronSSHIT ConsultantAuthor Commented:
Same local domain, yes.
Yes, send connector is set up and logging enabled. It is working properly.
Executing the command Test-ServiceHealth returns that all required services are running.

There were some errors in the Event Log for Exchange that stated a registry key was not accessible.
Event ID 10003: "The transport process failed during message processing with the following call stack: System.UnauthorizedAccessException: Access to the registry key 'HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ExchangeServer\v15\WorkerTaskFramework\IdStore\ProbeDefinitionIDConflicts' is denied."

I went in and modified the permissions on that key to be more inclusive and then rebooted but this did not fix the problem.

There are also a lot of Event ID 4999: "Watson report about to be sent for process id: 17032, with parameters: E12IIS, c-RTL-AMD64, 15.01.1466.003, edgetransport, mscorlib, M.W.RegistryKey.CreateSubKeyInternal, System.UnauthorizedAccessException, 15ca-dumptidset, 04.07.2117.000."
AaronSSHIT ConsultantAuthor Commented:
I followed the steps in this article and it resolved the mail flow issue!
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