Symptoms
O365 CSP installation.
Task "Unprovisioning "Tenant" for APS application Microsoft Office 365" fails:
500 Internal Server Error
"You cannot remove the initial domain created for you in Office 365."
Cause
Software-related issue APSA-13464: "Task 'Unprovisioning "Tenant" for APS application Microsoft Office 365' fails with 'You cannot remove the initial domain created for you in Office 365'".
Resolution
This issue was fixed in version 6.4 of Office 365 application. Please, consider upgrade of your Office 365 installation.