Thank you for posting this in Microsoft Q&A.
If you are the only Owner and only service administrator for the subscription then, you do not have to do anything.
This email is for customer who still have classic administrators in their tenant. And there are many customers who are still working with classic administrators to login to Azure portal.
Do not have to worry about this email if you do not have any classic administrators in your Azure subscription.
If you have already an account which has an owner role assigned then, you do not have to do anything.
If you want to assign owner role to any user in your Azure portal then you can follow below article,
Let me know if you have any further questions.
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