We have Active Directory, Domain Controller and Exchange server 2019 for abc.com. They are all behind NAT and all services (Autodiscover, ActiveSync, OWA, …) work properly.
We also need to have email service for xyz.com too, so this is what we've done so far:
External DNS
mail and autodiscover of xyz.com point to the same public IP address of abc.com.
Internal DNS
mail and autodiscover of xyz.com point to the same Exchange server as of abc.com.
Active Directory
xyz.com is defined as alternative UPN suffix in the properties of Active Directory Domains and Trusts.
Exchange Server
xyz.com is defined in the Accepted Domains of Exchange Server -> Mail Flow. Some email accounts are created with @xyz.com.
However, Autodiscover is not working for xyz.com email accounts. All clients we have tried fail to detect the server settings.
Again, Autodiscover works fine for main domain which is abc.com.
What we are trying to do is even possible?
Best Answer
I think you need to create the srv record.
I will create SRV record in abc.com DNZ zone, and all Autodiscover queries for xyz.com domain will be redirected to autodiscover.abc.com.
You could check this case https://social.technet.microsoft.com/Forums/exchange/en-US/97baf014-d036-47d2-8b97-24da1232aa53/autodiscover-dns-records-for-multiple-domain-names?forum=exchangesvrsecuremessaging