@app.route('/api/v1/wh/mg/lead/email/delivered', methods=['POST'])
def lead_email_delivered():
    """
    The lead email delivered webhook.
    :return: json
    """
    if request.method == 'POST':

        form_data = {
            "message_id": request.form.get('Message-Id', None),
            "x_mail_gun_sid": request.form.get('X-Mailgun-Sid', None),
            "domain": request.form.get('domain', 'email.com'),
            "event": request.form.get('event', 'delivered'),
            "timestamp": request.form.get('timestamp', None),
            "recipient": request.form.get('recipient', None),
            "signature": request.form.get('signature', None),
            "token": request.form.get('token', None)
        }

        # verify the mailgun token and signature with the api_key
        token = form_data['token'].encode('utf-8')
        timestamp = form_data['timestamp'].encode('utf-8')
        signature = form_data['signature'].encode('utf-8')
        mg_recipient = form_data['recipient']
        event = form_data['event']

        if verify(mailgun_api_key, token, timestamp, signature):

            try:
                lead = db_session.query(Lead).filter(
                    Lead.email_addr == mg_recipient
                ).first()

                if lead:

                    email = lead.email
                    lead_id = lead.id
                    event = form_data['event']

                    # set the delivered flags in the database
                    lead.followup_email_delivered = 1
                    lead.followup_email_status = event
                    lead.webhook_last_updated = datetime.now()
                    db_session.commit()

                    # return a successful response
                    return jsonify({
                        "l_id": lead_id,
                        "email": email,
                        "event": event,
                        "status": 'success'}), 202

                # return 404: no email for recipient email address
                else:
                    resp = {"Error": "Unable to resolve the recipient email address..."}
                    data = json.dumps(resp)
                    return Response(data, status=404, mimetype='application/json')

            # database exception
            except exc.SQLAlchemyError as db_err:
                resp = {"Database Error": str(db_err)}
                data = json.dumps(resp)
                return Response(data, status=500, mimetype='application/json')

        # signature and token verification failed
        else:
            resp = {"Signature": form_data['signature'], "Token": form_data['token']}
            data = json.dumps(resp)
            return Response(data, status=409, mimetype='application/json')

    # method not allowed
    else:
        resp = {"Message": "Method Not Allowed"}
        data = json.dumps(resp)
        return Response(data, status=405, mimetype='application/json')