How to set Contact as Send To details in email entity record in MS CRM?

function sendEmail()
{
	//Send To: Contact whose id is "8b4597d2-34c1-e711-810e-5065f38a9b91"
	var entityApiName = "contacts";
	var recordid= "8b4597d2-34c1-e711-810e-5065f38a9b91";

	var loggedInUserId = getUserId();
	var webapiPath = serverUrl + "/api/data/v8.0/emails";
	var email = {};
	email["subject"] = "Map notification: ";
	email["description"] = "Thank you.";
	var parties = [];
	//ActivityParty (From)
	var sender = {};
	sender["partyid_systemuser@odata.bind"] = "/systemusers(" + loggedInUserId + ")";
	sender["participationtypemask"] = 1; //From
	//add this to collection
	parties.push(sender);

	//if I comment following if condition (Send To), email record creates successfully
	//ActivityParty (To)
	if (entityApiName == "contacts" || entityApiName == "accounts" || entityApiName == "leads") {
		var receiver = {};
		receiver["partyid_account@odata.bind"] = "/" + entityApiName + "(" + recordid + ")";
		receiver["participationtypemask"] = 2; //To
		parties.push(receiver);
	}
	email["email_activity_parties"] = parties;

	$.ajax({
		type: "POST",
		contentType: "application/json; charset=utf-8",
		datatype: "json",
		url: webapiPath,
		data: JSON.stringify(email),
		async: false,
		beforeSend: function (XMLHttpRequest) {
			XMLHttpRequest.setRequestHeader("Accept", "application/json");
			XMLHttpRequest.setRequestHeader("Content-Type", "application/json; charset=utf-8");
			XMLHttpRequest.setRequestHeader("Prefer", "odata.include-annotations=*");
			XMLHttpRequest.setRequestHeader("OData-MaxVersion", "4.0");
			XMLHttpRequest.setRequestHeader("OData-Version", "4.0");
		},
		success: function (data, textStatus, XmlHttpRequest) {
			alert("Email saved successfully");
		},
		error: function (XMLHttpRequest, textStatus, errorThrown) {
			console.log(XMLHttpRequest);
		}
	});
}