check_address.py

# Load functions for validating email addresses
from email.utils import parseaddr
from dns.resolver import query
from dns.exception import DNSException

def check_address(addr):
  addr_parsed = parseaddr(addr)[1]
  
  # An empty string at this point means the address was wildly invalid
  if addr_parsed == '':
    return False

  # The parser accepts anything that is considered technically valid
  # according to RFC 822, so it still might not be addressable  
  if not '@' in addr_parsed:
    return False

  addr_domain = addr_parsed.rsplit('@', 1)[-1]
  
  if not '.' in addr_domain:
    return False

  # As a final check, look up the MX record for the domain.
  # If you're on a corporate LAN, make sure you test this with
  # internal email addresses! Sometimes internal DNS servers
  # don't have the company's own MX records set up properly.
  try:
    dns_check = bool(query(addr_domain, 'MX'))
    return dns_check
  except DNSException as exc:
    return False
  return True