On attempt to verify the Office 365 domain in CCP "Office 365 > Domains" tab, the following error message is displayed:
MS Graph API server error: 'Media type requires a ';' character before a parameter definition.'.
The error is caused by software-related issue APSA-18938
The issue has been permanently fixed in the Office 365 17.1.3 APS package. It is recommended to upgrade Office 365 package to the latest available version.
As a temporary workaround domains can be verified directly in Microsoft Online Portal, however this will not fix the error in the Customer Control Panel.