I am putting together a list of common mistakes made when configuring Hybrid Deployment. Items will be added to the list as I see them or are made aware of their existence, feel free to send me suggestions.
Always use the HCW (Hybrid Configuration Wizard) when configuring Hybrid Deployment.
Admin account not mail enabled
I think that this is probably the most common mistake, especially in hosted environments where multiple people from different organizations are administrators on the the Exchange Organization.
Always mail enable Exchange Admin accounts, or the wizard may fail during Set-HybridConfiguration or Update-HybridConfiguration.
You may see errors such as: “ERROR:Updating hybrid configuration failed with error 'Subtask ValidateConfiguration execution failed: Configure Legacy Exchange Support” as a symptom of the Admin account not being mail enabled.
DNS TXT record
When running the Hybrid Configuration Wizard, you are asked to create a DNS TXT record as proof of domain ownership. Do not ignore this step, as the wizard will fail in the end.
Create the record and wait 15-20 minutes before continuing.
Three strikes and you’re out
If the Hybrid Configuration Wizard fails for any reason; troubleshoot the problem instead of just running the wizard again. If configuring a hybrid relationship fails three times, you need to wait 24 hours before trying again.
I hope this will ease your planning and troubleshooting. Enjoy…