These are the basic steps we can follow for sending a basic message with smtplib:

1. To begin, we need to import the necessary classes: import smtplib.
2. The SMTP class represents a connection to an SMTP server. Next, we specify our email address, destination, and the message:

from_address = "[email protected]"
 to_address = "[email protected]"
 message = "Message"

3. To begin with the message format, we need to import the necessary classes:

from email.mime.text import MIMEText

4. These messages use the MIME standard, and so we must use the MIMEText class to build a plain text email. We implement an instance of the MIMEText class to build the message:   

mime_message = MIMEText(message, "plain")
mime_message["From"] = from_address
 mime_message["To"] = to_address
 mime_message["Subject"] = "Subject"

5. In case the message contains Unicode characters, consider specifying the encoding:

mime_message = MIMEText(message, "plain", _charset="utf-8")

6. You can modify the visual aspect of the message using HTML:

message = "<em>Hello</em>, <strong>python</strong>!"mime_message = MIMEText(message, "html", _charset="utf-8")

7. Once the message has been elaborated, we must make the connection to the SMTP server:             

import smtplib
 smtp = SMTP("smtp_server")

8. We can use the server address provided by your hosting provider for this. In the case of the most important services, the server addresses are smtp.live.com (Outlook/Hotmail), smtp.mail.yahoo.com (Yahoo!), and smtp.gmail.com (Gmail).
9. We then need to enter the data for authentication, that is, the username (usually, this is an email address) and password:smtp.login(from_address, "password")
10. Finally, we send the email and close the connection with the quit() method:

smtp.sendmail(from_address, to_address, mime_message.as_string())
smtp.quit()

In the following script, we are using a basic example for sending email using smtplib.

You can find the following code in the smtp_basic.py file:

#!/usr/bin/env python3

import smtplib

smtp = smtplib.SMTP('smtp_server')

try:
    smtp.sendmail('[email protected]', ['[email protected]'], "This is a test email message.")
except SMTPException as exception:
    print("Error: unable to send email: "+exception)
finally:
    smtp.quit()

In this script, we are using a SMTP object to connect to the SMTP server and then using the sendmail() method, passing from address, the destination address, and the message as parameters.

If you are using a webmail service (such as Gmail), your email provider must have provided you with outgoing mail server details that you can supply them with, as follows:

smtplib.SMTP('mail.server.domain', 25)

Here, we must point out that the third argument, message, is a string representing the email. We know that a message is usually composed of a header, sender, recipient, message content, and attachments.

In the following script, we are reviewing a way to send an email by using MIMeText for the message format. You can find the following code in the smtp_message_format.py file:

#!/usr/bin/env python3

import smtplib
from email.mime.text import MIMEText
from email.header import Header

sender = '[email protected]'
receiver = '[email protected]'

mail_host="smtp.domain.com"
mail_user="user" 
mail_password="password"

message = MIMEText('Python', 'plain', 'utf-8')
message['From'] = Header(sender, 'utf-8')
message['To'] = Header(receiver, 'utf-8')

subject = 'Python SMTP message'
message['Subject'] = Header(subject, 'utf-8')

smtp = smtplib.SMTP()

try:
    smtp.connect(mail_host, 25)
    smtp.login(mail_user,mail_password)
    smtp.sendmail(sender, receiver, message.as_string())
except smtplib.SMTPException as exception:
    print("Error:"+exception)
finally:
    smtp.quit()

If you get smtplib.SMTPNotSupportedError: SMTP AUTH, then the extension is not supported by the server. When you're trying this with a Gmail server, it's important to mention that Gmail requires TLS (which we will review in the following examples).