Alert Users when they try Self-Service Sign Up for PowerBI and PowerApps that their Admins might be in Trouble to manage Office 365 tenants.
Many Office 365 Admins have got in trouble when they tried to add their custom domains to their tenants but couldn't.
This is because the domains had already been added to unknown tenants without Admins after their users had conducted self-service sign up for PowerBI and PowerApps, and etc..
In this case, Admins need to log on to the unknown tenant first, and proceed "Verification your domain" step by adding DNS record to become an Admin.
After this, Admins change the signed-up users' domains of UPN to delete the custom domain.
Without knowing these facts, Admins try adding DNS records issued on the regular tenant again and again because verification fails and the new record is issued every time executing the confirmation button, which is the current behavior when the domain has already been added to any other Office 365 tenant.
This is a very big business impact for customers because it takes time to understand what's going on and sometimes cost to add DNS records.
Therefore, in a similar way of self-service sign up for Education plans, alert users before they try to sign up for PowerBI and PowerApps, and etc. that their Admins might be in trouble when they want to manage the domains in Office 365 tenants.