testing email functionality using sender and recipient with user-defined port number

test_email.py

#!/usr/bin/env python3

import os, sys, numpy, smtplib, logging, datetime
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from argparse import ArgumentParser

def test_simple_email( recipient, sender, port_number ):
    """
    send a simple test email from ``recipient`` to ``sender``, at ``port_number`` on the local machine, using the SMTP_ protocol.

    :param str recipient: the `RFC 2047`_ recipient's email with name.
    :param str sender: the `RFC 2047`_ sender's email with name.
    :param int port_number: a valid (:math:`1 \le`\ ``port_number`` :math:`\le 65535`) port number on the local machine.

    .. _`RFC 2047`: https://tools.ietf.org/html/rfc2047.html
    """
    assert( port_number > 0 )
    assert( port_number < 65536 )
    #
    ## first create the MIMEMultipart message
    email_text = '\n'.join(['This is a test email.', 'I hope it works!' ])
    msg = MIMEMultipart( )
    msg[ 'To'   ] = recipient
    msg[ 'From' ] = sender
    msg[ 'Subject'] = 'test email from %s to %s @ %s.' % ( sender, recipient, datetime.datetime.now( ).date( ).strftime( '%d %B %Y' ) )
    msg.attach( MIMEText( email_text, 'plain', 'utf-8' ) )
    #
    ## now send it out!
    smtp_conn = smtplib.SMTP('localhost', port_number )
    smtp_conn.ehlo( 'test' )
    smtp_conn.sendmail( msg['From'], [ msg["To"], ], msg.as_string( ) )
    smtp_conn.quit( )

if __name__=='__main__':
    #
    ## usage case is simple: test_email.py -R "name <email>" -S from argparse import ArgumentParser"name <email>" -P <port_number>
    parser = ArgumentParser( )
    parser.add_argument( '-R', '--recipient', dest='recipient', type=str, required = True,
                        help = 'The RFC 2047 (name <email>) form of the recipient.' )
    parser.add_argument( '-S', '--sender', dest='sender', type=str, required = True,
                        help = 'The RFC 2047 (name <email>) form of the sender.' )
    parser.add_argument( '-P', dest='port_number', type=int, default = 25,
                        help = 'The port number on location machine to test email sending functionality. Default is port 25.' )
    parser.add_argument( '--info', dest='do_info', action='store_true', default = False,
                        help = 'If chosen, then run with INFO logging.' )
    #
    args = parser.parse_args( )
    logger = logging.getLogger( )
    if args.do_info: logger.setLevel( logging.INFO )
    test_simple_email( args.recipient, args.sender, args.port_number )