Forum Discussion
Exchange Hybrid Configuration HCW8001 Unable to determine the Tenant Routing Domain
VasilMichev, thank you for your reply! I just found the solution. By default, Microsoft sets up a domain for customers, like company.onmicrosoft.com, which is automatically added to Exchange's Accepted Domains. In order for HCW to complete, it also needs a record with "mail" in it, like company.mail.onmicrosoft.com, added to Accepted Domains. Although both domains can be easily added to on-premises Exchange, only Microsoft support can add them to Exchange Online's Accepted Domains. I opened a support ticket, they added the domain, and HCW completed successfully.
FWIW: I think either the Entra Cloud Sync or the HCW is supposed to automatically add the "mail" domain because, in my test environment, it was automatically created. I suspect this is an intermittent bug that only affects some users, which would explain why the solution was hard to find.
VasilMichev, thank you for your reply! I just found the solution. By default, Microsoft sets up a domain for customers, like company.onmicrosoft.com, which is automatically added to Exchange's Accepted Domains. In order for HCW to complete, it also needs a record with "mail" in it, like company.mail.onmicrosoft.com, added to Accepted Domains. Although both domains can be easily added to on-premises Exchange, only Microsoft support can add them to Exchange Online's Accepted Domains. I opened a support ticket, they added the domain, and HCW completed successfully.
FWIW: I think either the Entra Cloud Sync or the HCW is supposed to automatically add the "mail" domain because, in my test environment, it was automatically created. I suspect this is an intermittent bug that only affects some users, which would explain why the solution was hard to find.
Yes, enabling dirsync should provision said domain, which is what the article you cited above is all about. Support can also fix it, so there you go :)