Customer Lockbox with service account

[MarkusDi]

Hi,

we would like to config Customer Lockbox at our customer with a service account and Mail relay to our servicedesk.

Which additional licenses besides "M365 Insider Risk Management" do we need? During licenses assignment I get this error: 

"The service Customer Lockbox requires OneDrive for Business (Plan 1), SharePoint Kiosk, SharePoint (Plan 2), SharePoint (Plan 1), Exchange Online Kiosk, Exchange Foundation, Exchange Online (Plan 2), Exchange Online (Plan 1) to be enabled as well."

Do we really need all of this?

I could not find any usefull documentation about this.

Thanks a lot

Markus

[#2]

until now I assumed that only those who process the requests need a license for "Customer Lockbox" but via a Microsoft support ticket i received this:
"Tenant level services can be very tricky when it comes to licensing. By the letter of the law, you probably should have an M365 E5 license for every user in your tenant if you are using this feature. It will work if you only have one though."

Can anyone confirm this?

Regards,
Markus