Why are some of my domains not eligible?
As you set up your email account, you might see some domains listed as not eligible or grayed out in your Email & Office Dashboard (for Office 365) or Workspace Control Center (for Workspace Email). This is because you can only have a one type of email account for each domain.
For example, you'll get an error message if you try to set up Office 365 with a domain that's already used by Workspace Email.
Office 365 can't be transferred to any other platforms. However, Workspace Email can be transferred to Office 365.