Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Hi John,
Thank you for providing the detailed error message. When you say “I am an office 365 user but we no longer use Outlook and the email system”, since you are not using Exchange online service, may I double confirm whether you had removed your custom domain from Office 365 Business subscription? See Remove a domain
Does this issue happen with every creating alias or specific alias?
Please provide us with the detailed information about Office 365 business subscription which you were using and tenant domain (e.g. @contoso.onmicrosoft.com) via the private message further analysis.
Moreover, may I know whether you get a chance to report it to Zoho support? If not, I would suggest please contacting them and see what they say. If they point out something on our side, please let us know.
I have sent you private message and here is the link to access it: https://answers.microsoft.com/en-us/privatemessages/list
Your patience and cooperation will be highly appreciated. Have a nice day and stay safe!
Best regards,
Shyamal