ECW and Mail Routing from Tenant to On Premise

When running the ECW it fails with the following error:

Update-HybridConfiguration
Failed

Error:
Updating hybrid configuration failed with error 'Subtask ValidateConfiguration execution failed: Configure Mail Flow

Also mail flow from my tenant to on premise has never successfully worked. The connectors were successfully created on premise and also in the tenant. However, the emails never make it on premise. The nonD reports: Remote Server returned '< #4.4.7 smtp;550 4.4.7 QUEUE.Expired; message expired>'

I'm more happy to provide additional logging and information, but would rather not do it in the public forum.

Thanks..