You have a Microsoft Exchange organization that uses an SMTP address space of contoso.com.

Several users use their contoso.com email address for self-service sign-up to Azure Active Directory (Azure AD).

You gain global administrator privileges to the Azure AD tenant that contains the self-signed users.

You need to prevent the users from creating user accounts in the contoso.com Azure AD tenant for self-service sign-up to Microsoft 365 services.

Which PowerShell cmdlet should you run?

A. Set-MsolCompanySettings

B. Set-MsolDomainFederationSettings

C. Update-MsolfederatedDomain

D. Set-MsolDomain

Reference:
https://docs.microsoft.com/en-us/azure/active-directory/enterprise-users/directory-self-service-signup