To add a domain to our tenant.

Hello, @IniobongNkanga-8038,

Welcome to the Microsoft Q&A platform!

The issue you are experiencing may be because someone has previously signed up for Microsoft 365 using the domain's email address. Here are some steps to resolve this issue:

1.Verify Domain Ownership: Ensure that you have ownership of the domain. You can do this by checking the domain's DNS records and confirming that you have administrative access to the domain's settings.

2.Check for Existing Associations: Sometimes, domains can be inadvertently associated with other tenants. You can try to identify if the domain is linked to any other tenant by using the Microsoft 365 admin center.

3.Remove Domain from Other Tenant: If you find that the domain is associated with another tenant, you will need to remove it from that tenant. This typically involves changing the primary email addresses of users in the old tenant to a different domain (e.g., the default onmicrosoft.com domain) and then removing the domain from the old tenant. Once the domain is free, you can add it to your new tenant.

(Notice: If you find that the domain is being used by individual accounts within your tenant, a global administrator can disassociate those accounts and then add the domain to the tenant.)

For more detailed guidance, you can refer to https://zcusa.951200.xyz/en-us/microsoft-365/admin/setup/add-domain?view=o365-worldwide and https://zcusa.951200.xyz/en-us/microsoft-365/admin/get-help-with-domains/find-and-fix-issues?view=o365-worldwide.

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Thank you for your support and understanding.

Best Wishes,

Alex Zhang