Test your SMTP settings

test_smtp.py

import smtplib
import base64

user = 'bob'
password = 'password'

# The server handle TLS connection, not the boring STARTTLS upgrade
server = smtplib.SMTP_SSL(host='smtp.example.com', timeout=5)
server.ehlo() # the server say its name and handled commands, you should see "AUTH PLAIN"
# The RFC for SMTP doesn't say wich text encoding must be used, smtplib use low ASCII, lets forge the command
server.docmd("AUTH PLAIN", b64encode(f"\0{user}\0{password}".encode("utf8")).decode("ascii"))