Send email via SMTP. It works with Gmail.

sendmail.py

#!/usr/bin/env python3

import smtplib
import argparse
import os
import sys

def send_email(
    host: str, 
    username: str, 
    password: str, 
    receiver: str, 
    subject: str,
    text: str
):
    message = ""
    message += f"From: {username.split('@')[0]} <{username}>\n"
    message += f"To: {receiver.split('@')[0]} <{receiver}>\n"
    message += f"Subject: {subject}\n\n"
    message += text

    server = smtplib.SMTP(host)
    server.connect(host, 587)
    server.starttls()
    server.login(username, password)
    server.sendmail(username, receiver, message)
    server.quit()


if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument("--host", required=False, help="SMTP server host")
    parser.add_argument("--username", required=False, help="SMTP username")
    parser.add_argument("--password", required=False, help="SMTP password")
    parser.add_argument("--receiver", "--to", "-r", required=True, help="Email receiver")
    parser.add_argument("--subject", "-s", required=True, help="Email subject")
    parser.add_argument("--text", "-t", required=True, help="Email text")
    args = parser.parse_args()

    # try to find  HOST, USERNAME, PASSWORD from environment variables
    host = args.host or os.environ.get("ES_HOST")
    username = args.username or os.environ.get("ES_USERNAME")
    password = args.password or os.environ.get("ES_PASSWORD")

    if not host or not username or not password:
        print("Please provide host, username, password", file=sys.stderr)
        exit(1)

    send_email(
        host=host,
        username=username,
        password=password,
        receiver=args.receiver,
        subject=args.subject,
        text=args.text
    )