Added new domain for email in Microsoft 365. Able to add new domain email accounts as alias in current primary (different) domain. 9 of 10 successful. One gave this error:
"An Azure Active Directory call was made to keep object in sync between Azure Active Directory and Exchange Online. However, it failed. Detailed error message: Another object with the same value for property proxyAddresses already exists."
I tried sending email to the email address in question and got the standard message "email name not found at domain.com" This would seem to indicate there is no account by that name. I have tried for two days with no difference, same error.
Has anyone a solution for this?