smtpDataError(550)for sending email

Question

import os
import smtplib, ssl


def send_mail(msg) :
    host = "smtp.gmail.com"
    port = 465

    user_mail = "[email protected]"
    password = os.getenv("News_Pass")

    receiver = "[email protected]"
    context = ssl.create_default_context()

    with smtplib.SMTP_SSL(host=host,port=port,context=context) as server:
        server.login(user_mail,password)
        server.sendmail(user_mail,receiver,msg)

I want to send email using python code, but I get the following error: smtpDataError(550). What should I do?