The prompt appears because the old Cox.net address is still associated with a Microsoft account sign-in or alias somewhere in the account setup.
To stop it:
- Sign in to the Microsoft account that is still being prompted.
- Open Edit account info: Edit account info
- Check the email addresses listed for that account.
- If possible, add the Gmail address as an alias by selecting Add email and following the prompts.
- Set the new address as the primary alias.
- Remove the old Cox.net address if it is still listed and no longer needed.
Important details:
- Microsoft account email addresses are aliases that share the same account settings, subscriptions, and password.
- An email address can only be used with one Microsoft account.
- If the Gmail address was used to create a completely separate Microsoft account, it cannot also be added as an alias to the old account.
- If a sign-in screen says “Which account do you want to use?”, that means the same email address exists as both a personal account and a work or school account. One documented way to reduce that prompt is to rename the personal Microsoft account by changing its primary alias.
- If sign-in or alias changes are blocked because security information was recently changed, those changes can be temporarily unavailable until the protection period ends.
If access to the old account is no longer possible, use the Sign-in helper or Contact Support options provided in Microsoft account support.
- Change the email address for your Microsoft account
- How to add an email address to your Microsoft account
- Which account do you want to use?
- Microsoft Account. Trying to change my primary email address. - Microsoft Q&A
- The user name for my Microsoft account is an email address that I no longer use or can access. How can I change my user name to my current email address? - Microsoft Q&A