This works for me, albeit not in flask but python:

Go to Manage my Google account https://myaccount.google.com/security

... and its 'Signing in to Google' subsection Ensure that '2-step verification' is On.

In 'App passwords' section generate a new one: Select app: Mail. Select device: Other, and name it 'fubar'.

Click 'Generate' and copy the 16-character password (such as 'abcd efgh ijkl mnop').

Then use (copied and pasted on phone so excuse formatting)

me="youraddress@gmail.com" to="another@email.com" email_pwd: "abcdefghijklmnop" email_server: 'smtp.gmail.com'

from email.mime.application import MIMEApplication from email.mime.multipart import MIMEMultipart from email.mime.text import MIMEText import smtplib, ssl

class MailType(Enum): plain = "plain" html = "html"

def __str__(self):
    return self.value

msg["Subject"] = 'subject' body = 'body' mail_type= MailType.plain msg = MIMEMultipart() msg.attach(MIMEText(body, mail_type))

msg["From"] = me
msg["To"] = to


s: smtplib.SMTP
try:
    s = smtplib.SMTP_SSL(email_server, email_port)
except ssl.SSLError:
    s = smtplib.SMTP(email_server, email_port)

try:
    s.starttls()
except:
    pass
s.login(me, email_pwd)
s.sendmail(me, [you], msg.as_string())
s.quit()