When helping our clients with Office 365 deployments, we sometimes find that DirSync has been associated with a trial tenant that is about to expire and/or was originally created with a provisional name, or similar. In any case, a public DNS name can only be verified once in Office 365, which associates that namespace with the Office 365 and Azure AD tenancies. So if we want to move DirSync (which is also a prerequisite for ADFS) to a new tenancy, then we need to back it out from the first tenant and re-associate it with the second. Unfortunately, that process isn’t exceptionally quick, but there are some manual steps that you can carry out in order to accelerate the change. As we do this more often, our list of things to check is growing, so this list may change, but this is where we’re at today. Please feel free to comment if you feel we’re overlooking anything.