Set sensitivity label on mail message using graph api

Hi,

It is possible to set Microsoft Information Protection sensitivity labels by appending a singleValueExtendedProperties block, although in a slightly different way that Glen mentions above. You'll need:

• Entra tenant ID
• The human-readable name of your sensitivity label
• The GUID associated with that label. This can be obtained from the M365 admin interface or using a browser's dev tools to view the response from PolicyHandler.ashx?action=getpolicylabels when assigning a label to a Word document, for example

This is the updated request body...

{
"message": {
    "subject": "Meet for lunch?",
    "body": {
        "contentType": "Text",
        "content": "The new cafeteria is open."
    },
    "toRecipients": [
        {
            "emailAddress": {
                "address": "******@domain.com"
            }
        }
    ],
    "singleValueExtendedProperties": [  
        {
            "id":  "String {00020386-0000-0000-C000-000000000046} Name msip_labels",
            "value": "MSIP_Label_<SENSITIVITY_LABEL_GUID>_Enabled=True;MSIP_Label_<SENSITIVITY_LABEL_GUID>_SiteId=<ENTRA_TENANT_ID>;MSIP_Label_<SENSITIVITY_LABEL_GUID>_SetDate=<ISO_8601_TIMESTAMP>;MSIP_Label_<SENSITIVITY_LABEL_GUID>_Name=<SENSITIVITY_LABEL_NAME>;MSIP_Label_<SENSITIVITY_LABEL_GUID>_ContentBits=1;MSIP_Label_<SENSITIVITY_LABEL_GUID>_Method=Privileged;"
        }
    ]
}

This is a Powershell representation of the message object, where it's perhaps easier to read the singleValueExtendedProperties details:

$timeStamp = (Get-Date -Format "yyyy-MM-ddTHH:mm:ss.fffZ")
$tenantId = "11111111-1111-1111-1111-111111111111"
$label = @{
    name = "Confidential"
    guid = "22222222-2222-2222-2222-222222222222"
}
$emailPayload = @{
    message = @{
        subject = "Meet for lunch?"
        body = @{
            contentType = "Text"
            content = "The new cafeteria is open."
        }
        toRecipients = @(
            @{
                emailAddress = @{
                    address = "******@domain.com"
                }
            }
        )
        singleValueExtendedProperties = @(
            @{
                id = "String {00020386-0000-0000-C000-000000000046} Name msip_labels"
                value = "MSIP_Label_$($label.guid)_Enabled=True;`
                    MSIP_Label_$($label.guid)_SiteId=$($tenantId);`
                    MSIP_Label_$($label.guid)_SetDate=$($timeStamp);`
                    MSIP_Label_$($label.guid)_Name=$($label.name);`
                    MSIP_Label_$($label.guid)_ContentBits=1;`
                    MSIP_Label_$($label.guid)_Method=Privileged;"
            }
        )
    }
}

Hope that's useful.