Office 365 user creation wizard allows to finish the creation when the domain is not verified on Microsoft side, as result we are getting the error:
[Plesk::APS::processScriptExecutionResult] Error message returned by verification script for setting with id up_UserPrincipalName: Domain XXX.com is not registered for use with Microsoft Online Services. Please add domain in Configuration of services before adding users of this domain.
This issue was submitted to the Maintenance Team as APSA-4796: "Graceful handling of users with UPN on domains not registred in Office365". It will be implemented in one of future versions of Office365 APS package.
Please contact your TAM or PTA to trace the status of this request.