Email with CRM records available or without(directly using email Id) | Microsoft Dynamics 365 Sample

email.json

{
    "regardingobjectid_contact@odata.bind": "/contacts(<regarding contact record guid>)",
    "subject": "Email Subject",
    "description": "Email Description",
    "email_activity_parties": [
        {
            "partyid_systemuser@odata.bind": "/systemusers(<from system user record guid>)",
            "participationtypemask": 1
        },
        {
            "partyid_contact@odata.bind": "/contacts(<to contact record guid>)",
            "participationtypemask": 2
        },
        {
            "addressused": "<Cc email id>",
            "participationtypemask": 3
        },
        {
            "addressused": "<Bcc email id>",
            "participationtypemask": 4
        }
    ]
}