
Hi @Cams ,
Thanks for your detailed explanation.
The green domain you created is an onmicrosoft.com fallback domain in Microsoft 365.
It serves as a default email routing address for your Microsoft 365 environment. When a user is set up with a mailbox, email is routed to the fallback domain. Even if a custom domain is used (for example, tailspintoys.com), if that custom domain is deleted from your Microsoft 365 environment, the fallback domain ensures that your user's email is successfully routed.
Reference:https://learn.microsoft.com/en-us/microsoft-365/admin/setup/add-or-replace-your-onmicrosoftcom-domain?view=o365-worldwide
A sharepoint tenant can only have one Top-level SharePoint site. You cannot create sites using another domain.
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