Check the validation of an email

check_email.py

# encoding: utf8

"""
Created on 2017.06.27

@author: yalei

Reference:
1. http://www.ruanyifeng.com/blog/2017/06/smtp-protocol.html
2. http://blog.online-domain-tools.com/2014/11/14/how-to-verify-email-address/
"""

import sys
import dns.resolver
from smtplib import SMTP


def check_mail(email, timeout=30):
    domain = email.split('@')[-1]
    try:
        mx = dns.resolver.query(domain, 'MX')
        server = list(mx)[0].exchange.to_text().rstrip('.')
    except dns.resolver.NXDOMAIN as e:
        return False, str(e)
    try:
        smtp = SMTP(server, timeout=timeout)
        status_code, msg = smtp.helo(domain)
        if status_code != 250:
            smtp.quit()
            return False, msg

        status_code, msg = smtp.docmd('MAIL FROM:<webmaster@python.org>')
        if status_code != 250:
            smtp.quit()
            return False, msg

        status_code, msg = smtp.docmd("RCPT TO:<%s>" % email)
        if status_code != 250:
            smtp.quit()
            return False, msg
        smtp.quit()
        return True, ''
    except Exception as e:
        return False, str(e)


if __name__ == '__main__':
    # test
    if len(sys.argv) == 2:
        e = sys.argv[1]
        print('[%s] is valid: %s' % (e, check_mail(e)[0]))
        sys.exit()

    normal_emails = ['python-tornado@googlegroups.com',
                     'webmaster@python.org']
    print('Check normal emails:')
    for e in normal_emails:
        print('[%s] is valid: %s' % (e, check_mail(e)[0]))

    error_emails = ['python-tornado@gmail.com',
                    '12312eqwdsarfAFD@python.org']
    print('\nCheck error emails:')
    for e in error_emails:
        print('[%s] is valid: %s' % (e, check_mail(e)[0]))