Hello KevinDWhite
Hi, I'm Karl and will be happy to help you today.
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How do I setup a custom email address domain using a domain that is registered with a registrar other than GoDaddy?
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Short answer is that you can't. Using a Personalized email address with a <Premium> Outlook.com account (part of MS 365) requires the use of a domain registered with GoDaddy in order to send/receive emails via an Outlook.com account. Your only option is to move the domain to GoDaddy as the registrar for the domain.
Get a personalized email address in Microsoft 365
https://support.microsoft.com/en-us/office/get-...
Am sure this isn't the answer you're looking for but it's the only one that applies to the question asked. Can't provide a solution that doesn't exist. If one did, rest assured that I would have provided it.
Just so there is no misunderstanding, this is a public user-to-user support forum. We're users just like you helping other users. We do not work for Microsoft and have no input on Microsoft's policies, procedures, or design decisions. Microsoft Support personnel do not staff this forum.