MS Graph API - set message sensitivity to 'Confidential'

Hi, 

I need to send confidential emails using the MS Graph API and I tried to accomplish this by using a legacy extended property:

"singleValueExtendedProperties": [ { "Id": "Integer 0x0036", "Value": "3" } ]

But this only adds an informative label to the message - "Please treat this as Confidential." - but the actual sensitivity of the email is Unrestricted.

Is there another way to send confidential emails via MS Graph or, if not, is this feature planned for future implementation?

Thank you!