When you try to verify a domain in Microsoft Office 365, you receive one of the following error messages:
<DomainName> has already been verified for your account, or for another Microsoft Online Services account.
Can't verify the domain
<DomainName> was already added to a different Office 365 account domain.onmicrosoft.com.
Sign in to that account as an admin, and remove domain <DomainName>. Then come back here and try adding <DomainName> to this account again
<DomainName> was already added to a different Office 365 account domain.onmicrosoft.com.
Sign in to that account as an admin, and remove domain <DomainName>. Then come back here and try adding <DomainName> to this account again