Simple debug mail server

mailserver.py

#!/usr/bin/env python3
import argparse
import asyncore
import email.header
import email.parser
import smtpd

def decodeHeader (value):
    return email.header.make_header(email.header.decode_header(value))

class DebugServer (smtpd.SMTPServer):
    def process_message (self, peer, mailfrom, rcpttos, data, **kwargs):
        print('-' * 60)
        if isinstance(data, bytes):
            data = data.decode()

        message = email.parser.Parser().parsestr(data)
        for k, v in message.items():
            print('{}: {}'.format(k, decodeHeader(v)))

        print()
        print(message.get_payload(decode=True).decode())


def main ():
    parser = argparse.ArgumentParser(description='Simple debug SMTP server.')
    parser.add_argument('host', default='localhost', nargs='?', help='Server host')
    parser.add_argument('port', default=8025, nargs='?', help='SMTP port')
    args = parser.parse_args()

    server = DebugServer((args.host, args.port), None)
    print('Started debug SMTP server on {}:{}'.format(args.host, args.port))
    asyncore.loop(timeout=2)

if __name__ == '__main__':
    main()