I'm new to posting but have been following discussions for a while. I need help with a client's setup for an Exchange Hybrid arrangement with Microsoft 365. I've completed some initial steps, including adding the domain suffix 'domain.com' to our on-premises Active Directory. Right now, I'm stuck on the second step: installing Entra ID Connect. After that, I plan to run the Exchange Hybrid Configuration Wizard using the Full Hybrid approach, as we want to continue routing mail through the on-premises Exchange.
However, I'm concerned about added complications. We have already verified the 'company.com' domain in Microsoft 365, but we haven't changed any DNS settings yet. I have a theory that since Autodiscover is still pointing to our on-premises Exchange, devices using EAS and Outlook on Windows are having issues authenticating because they're trying to log in to accounts that aren't on Microsoft 365 yet. Can anyone guide me on how to properly add 'company.com' to Microsoft 365 without disrupting current authentication processes?
3 Answers
Just a thought, but have you considered why they want to go for a hybrid setup instead of moving fully to the cloud? They might want to start integrating a few users gradually and test everything without giving up their legacy systems right away.
Outlook tends to check Microsoft 365 during auto-discover, which is likely why you're seeing authentication issues. There's a workaround where you can adjust the registry settings in classic Outlook to change how it handles these requests, but it's tricky.
I've already tried that method, but it doesn’t seem to take effect. All users are on classic Outlook.
Before you proceed with adding the domain to Microsoft 365, I recommend holding off until Entra ID Connect is properly installed and syncing identities. If you add the domain prematurely, autodiscover and modern authentication could direct to cloud endpoints, which might break your on-premises authentication.
Do I really need to wait? I thought I had to add the domain during the setup process. Could using a dummy domain work instead?
Exactly! It's probably because they want to take their time or are just unsure about the full transition yet. Can't just toss out what they know!