Flask Mail & GMail Settings - Very Confused - ssl

Question

I have been learning Flask (with the help of many very generous YouTuber's)
I thought adding a 'Subscribe' function that sends an email notification via GMail would be fairly straightforward.
After a few days of Googling around I am getting the following results from each combination of port 465 or 587, SSL and/or TLS enabled/disabled.
Less secure apps option in Gmail is permitted.
from flask import Flask
from flask_mail import Mail, Message
app = Flask(__name__)
app.config['MAIL_DEBUG'] = True
app.config['TESTING'] = False
app.config['MAIL_SERVER'] = 'smtp.gmail.com'
app.config['MAIL_PORT'] = see results below
app.config['MAIL_USE_TLS'] = see results below
app.config['MAIL_USE_SSL'] = see results below
app.config['MAIL_USERNAME'] = None
app.config['MAIL_PASSWORD'] = 'secret_password'
app.config['MAIL_DEFAULT_SENDER'] = 'me#gmail.com'
app.config['MAIL_MAX_EMAILS'] = None
app.config['MAIL_SUPPRESS_SEND'] = False
app.config['MAIL_ASCII_ATTACHMENTS'] = False
mail = Mail(app)
#app.route('/')
def home():
msg = Message('Test Message from Flask Mail', recipients=['you#gmail.com'])
mail.send(msg)
return 'OK'
if __name__ == '__main__':
app.run(debug=True)
Results in -
Port SSL TLS Result
465 On On smtplib.SMTPNotSupportedError: STARTTLS extension not supported by server
465 Off On smtplib.SMTPServerDisconnected: Connection unexpectedly closed
465 On Off smtplib.SMTPSenderRefused: (530, b'5.7.0 Authentication Required
465 Off Off smtplib.SMTPServerDisconnected: Connection unexpectedly closed
587 On On ssl.SSLError: [SSL: WRONG_VERSION_NUMBER] wrong version number
587 Off On smtplib.SMTPSenderRefused: (530, b'5.7.0 Authentication Required
587 On Off ssl.SSLError: [SSL: WRONG_VERSION_NUMBER] wrong version number
587 Off Off smtplib.SMTPSenderRefused: (530, b'5.7.0 Must issue a STARTTLS command first
SSL version is -
import ssl
ssl.OPENSSL_VERSION
'OpenSSL 1.1.1f 31 Mar 2020'
This SMTPLIB works just fine -
import smtplib
smtp_server = 'smtp.gmail.com'
port = 587
sender = 'me#gmail.com'
password = 'secret'
receiver = 'you#gmail.com'
msg = "Test Message from SMTPLIB"
server = smtplib.SMTP(smtp_server, port)
server.starttls()
server.login(sender,password)
server.sendmail(sender, receiver, msg)

Answer 1

It's been a few years now but worked for me (looking at an old code) was
app.config['MAIL_PORT'] = 587
app.config['MAIL_USE_TLS'] = True
app.config['MAIL_USE_SSL'] = False
app.config['MAIL_USERNAME'] = <your email address> # should not be None as you currently have in your code
Note: I only used this code for testing on my local machine. I switched to Google App Engine mail and later SendGrid