The server receives the messages from the clients and logs them to the console.

Listing 5.9a gives the code for the SMTP server as follows:

#!/usr/bin/env python 
# Python Network Programming Cookbook, Second Edition -- Chapter - 5 
# This program is optimized for Python 2.7.12 and Python 3.5.2. 
# It may run on any other version with/without modifications. 
 
import smtplib 
import email.utils 
import argparse 
from email.mime.text import MIMEText 
 
def mail_client(host, port, fromAddress, toAddress, subject, body): 
    msg = MIMEText(body) 
    msg['To'] = email.utils.formataddr(('Recipient', toAddress)) 
    msg['From'] = email.utils.formataddr(('Author', fromAddress)) 
    msg['Subject'] = subject 
 
    server = smtplib.SMTP(host, port) 
    server.set_debuglevel(True)   
    try: 
        server.sendmail(fromAddress, toAddress, msg.as_string()) 
    finally: 
        server.quit() 
 
 
if __name__ == '__main__': 
    parser = argparse.ArgumentParser(description='Mail Server Example') 
    parser.add_argument('--host', action="store", 
    dest="host", type=str, required=True) 
    parser.add_argument('--port', action="store", 
    dest="port", type=int, required=True) 
    parser.add_argument('--fromAddress', action="store", 
    dest="fromAddress", type=str, required=True) 
    parser.add_argument('--toAddress', action="store", 
    dest="toAddress", type=str, required=True) 
    parser.add_argument('--subject', action="store", 
    dest="subject", type=str, required=True) 
    parser.add_argument('--body', action="store", 
    dest="body", type=str, required=True) 
    given_args = parser.parse_args() 
    mail_client(given_args.host, given_args.port, 
    given_args.fromAddress, given_args.toAddress, 
    given_args.subject, given_args.body) 

Listing 5.9b gives the code for the SMTP client as follows:

#!/usr/bin/env python 
# Python Network Programming Cookbook, Second Edition -- Chapter - 5 
# This program is optimized for Python 2.7.12 and Python 3.5.2. 
# It may run on any other version with/without modifications. 
 
import smtpd 
import asyncore 
import argparse 
 
class CustomSMTPServer(smtpd.SMTPServer): 
     
    def process_message(self, peer, mailfrom, rcpttos, data): 
        print ('Message Received from:', peer) 
        print ('From:', mailfrom) 
        print ('To  :', rcpttos) 
        print ('Message :', data) 
        return 
 
if __name__ == '__main__': 
    parser = argparse.ArgumentParser(description='Mail Server Example') 
    parser.add_argument('--host', action="store", 
    dest="host", type=str, required=True) 
    parser.add_argument('--port', action="store", 
    dest="port", type=int, required=True) 
    given_args = parser.parse_args() 
    server = CustomSMTPServer((given_args.host, given_args.port), None) 
    asyncore.loop() 

You may run the server and client code. The server handles the emails from the clients, as follows:

$ python 5_9a_mail_server.py --host='127.0.0.1' --port=1025
    
Message Received from the peer: ('127.0.0.1', 47916)
Addressed from: [email protected]
Addressed to  : ['[email protected]']
Message : Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
To: Recipient <[email protected]>
From: Author <[email protected]>
Subject: Hi, Hello
    
$ python 5_9b_mail_client.py --host='127.0.0.1' --port=1025 [email protected] [email protected] --subject="Hi, Hello" --body="Good to see you all. Keep in touch. Take Care"
send: 'ehlo [127.0.1.1]
'
reply: b'250-llovizna
'
reply: b'250-SIZE 33554432
'
reply: b'250 HELP
'
reply: retcode (250); Msg: b'llovizna
SIZE 33554432
HELP'
send: 'mail FROM:<[email protected]> size=232
'
reply: b'250 OK
'
reply: retcode (250); Msg: b'OK'
send: 'rcpt TO:<[email protected]>
'
reply: b'250 OK
'
reply: retcode (250); Msg: b'OK'
send: 'data
'
reply: b'354 End data with <CR><LF>.<CR><LF>
'
reply: retcode (354); Msg: b'End data with <CR><LF>.<CR><LF>'
data: (354, b'End data with <CR><LF>.<CR><LF>')
send: b'Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
To: Recipient <[email protected]>
From: Author <[email protected]>
Subject: Hi, Hello

Good to see you all. Keep in touch. Take Care
.
'
reply: b'250 OK
'
reply: retcode (250); Msg: b'OK'
data: (250, b'OK')
send: 'quit
'
reply: b'221 Bye
'
reply: retcode (221); Msg: b'Bye' 

The output is depicted by the following screenshot: