wrong email being used for M365 sign on

Question

I am about to loose access to an old blueyonder email address which is used to sign into my M365 account. When I try to use my new outlook.com email address via 'add a username' it says I already have an account with that email.

How do I swap my existing blueyonder M365 subscription to point to my outlook.com one without loosing emails/M365 subscription data (eg onedrive/excel etc)?

thanks

Answer 1

Hello

Microsoft won't allow using an EXISTING outlook.com address as alias for another Microsoft account, because that outlook.com address is already its own Microsoft account. It is explained here: https://support.microsoft.com/en-us/office/add-or-remove-an-email-alias-in-outlook-com-459b1989-356d-40fa-a689-8f285b13f1f2

Go to your account online, then go to Your Info > Sign in preference, Add an alias.

You have two options here:

Create new: this will allow you to use the native domain outlook.com to create a new alias. (this is to create a new outlook.com address, not an existing one)

Add existing: this will allow you to add a 3rd party email address, such as yahoo, gmail, as long as they are not already associated with another Microsoft account.

Once added, make this new alias your primary alias, then you can delete the other email as alias, and that email is free from this Microsoft account instantly.

Most importantly, you want to go to Security > Manage how I sign in, make sure you update it here. This is what woudl be used to send you the 2FA code. Here you actually can add an existing outlook.com address.

Answer 2

The existing Outlook.com address is already its own Microsoft account, and Microsoft does not support merging Microsoft accounts. Because of this, the Outlook.com address cannot be added as a sign-in alias to the existing blueyonder-based Microsoft account, and the M365 subscription, OneDrive, and other data tied to the blueyonder account cannot be moved onto the Outlook.com account.

The only supported options are:

1. Keep using the current Microsoft account (with blueyonder as the username) and add a different alias
   • Go to Manage how you sign in to the Microsoft account: Manage sign-in preferences.
   • Add a new alias that is not already a Microsoft account (for example, a different email address or a new Outlook.com address created there).
   • Set that new alias as the primary alias.
   • This lets that account keep all existing M365/OneDrive data while signing in with the new alias instead of the blueyonder address.
2. Free up a third‑party email address from another Microsoft account (if applicable)
   • If there is a third‑party email (like Gmail) currently used as the username of a different Microsoft account and there is no data or purchases on that account, it can be freed and then added as an alias to the main account:
     1. Sign in to the other Microsoft account and go to Your info → Sign-in preferences.
     2. Add a new alias (for example, a new Outlook.com address), make it the primary alias, then remove the third‑party email alias so it becomes available.
     3. Close that now-empty Microsoft account if desired.
     4. Add that freed email as an alias to the main account and optionally make it primary.
   • This does not move any data or subscriptions; it only reuses the email address as a sign-in alias on the desired account.

Key limitations based on current behavior:

• Existing Outlook.com addresses cannot be moved from one Microsoft account to another.
• Microsoft accounts cannot be merged; subscriptions, OneDrive content, and other data remain bound to the original account.
• Removing an Outlook.com alias from an account permanently deletes that alias and it cannot be attached to another Microsoft account later.

To avoid losing access when the blueyonder mailbox is closed, configure a new alias on the current Microsoft account (option 1) and use that alias for future sign-in and security info. The M365 subscription and data will remain on that same underlying account.

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References:

• How do I merge my OneDrive for home with my OneDrive for work or school ?
• Which account do you want to use?
• Add or remove an email alias in Outlook.com
• Connecting a Microsoft subscription to Outlook
• How to add an existing outlook.com account to my existing microsoft account? - Microsoft Q&A
• I realize I have 2 different accounts. How do I combine the 2? - Microsoft Q&A