How Do You Send an Email Using SMTP in Python?

Sending emails programmatically is a common requirement for many applications, whether it’s to send notifications, alerts, or verification emails. In Python, you can send emails using the SMTP (Simple Mail Transfer Protocol) with the help of the built-in smtplib library. This article will guide you through the steps to send an email using SMTP in Python.

What is SMTP?

SMTP (Simple Mail Transfer Protocol) is a communication protocol used for sending emails over the internet. It allows your application to connect to an email server and transmit messages to recipients.

Prerequisites

Before you start sending emails, you’ll need:

1. An SMTP server address (e.g., smtp.gmail.com for Gmail).
2. A valid email account (sender’s email address).
3. The recipient’s email address.
4. SMTP authentication credentials (email and password for the sender’s account).

Steps to Send an Email Using SMTP in Python

Here’s a step-by-step guide:

1. Import Required Libraries

The main library used is smtplib, and for composing the email, you can use email.message or email.mime modules.

import smtplib
from email.mime.text import MIMEText
from email.mime.multipart import MIMEMultipart

2. Set Up SMTP Server Details

Define the SMTP server and port number. Common SMTP servers include:

• Gmail: smtp.gmail.com (port 587 for TLS or 465 for SSL)
• Outlook: smtp.office365.com
• Yahoo: smtp.mail.yahoo.com

3. Write Your Email

Create the email’s content, including the sender, recipient, subject, and message body. Use MIMEMultipart for more flexibility (e.g., adding attachments or formatting).

4. Authenticate and Send

Log in to the SMTP server with your credentials and send the email.

Code Example: Sending a Simple Email

Here’s a full example of sending an email using Gmail’s SMTP server:

import smtplib
from email.mime.text import MIMEText
from email.mime.multipart import MIMEMultipart

# Sender and Receiver Email Addresses
sender_email = "[email protected]"
receiver_email = "[email protected]"
password = "your_email_password"

# Create the Email
subject = "Test Email from Python"
body = "This is a test email sent using Python and SMTP."

# Create a MIME object
message = MIMEMultipart()
message["From"] = sender_email
message["To"] = receiver_email
message["Subject"] = subject

# Attach the email body
message.attach(MIMEText(body, "plain"))

# Connect to SMTP Server and Send Email
try:
    # Use Gmail's SMTP server with TLS
    with smtplib.SMTP("smtp.gmail.com", 587) as server:
        server.starttls()  # Start TLS encryption
        server.login(sender_email, password)  # Login to your account
        server.sendmail(sender_email, receiver_email, message.as_string())  # Send email
        print("Email sent successfully!")
except Exception as e:
    print(f"Failed to send email: {e}")

Code Breakdown

1. Set Up Sender and Receiver Details:
   • Replace [email protected] and [email protected] with actual email addresses.
   • Replace your_email_password with the sender’s email account password.
2. Create the Email:
   • Use MIMEMultipart to build the email structure (e.g., adding subject, body, attachments).
   • Attach the plain text body using MIMEText.
3. Connect to the SMTP Server:
   • Use the smtplib.SMTP class to connect to the server.
   • Use starttls() to enable encryption.
   • Log in using server.login().
4. Send the Email:
   • Call server.sendmail() with the sender, receiver, and email content.

Sending Emails with Attachments

To send an email with an attachment, include the following steps:

1. Import the MIMEBase and encoders modules.
2. Add the file as an attachment using MIMEBase.
3. Encode the file and attach it to the email.

Example:

from email.mime.base import MIMEBase
from email import encoders

# Add an attachment
filename = "example.pdf"  # Replace with your file path
with open(filename, "rb") as attachment:
    part = MIMEBase("application", "octet-stream")
    part.set_payload(attachment.read())

# Encode the file in ASCII
encoders.encode_base64(part)
part.add_header(
    "Content-Disposition",
    f"attachment; filename= {filename}",
)

# Attach the file to the email
message.attach(part)

Notes:

1. Enable Less Secure Apps:
   • Some email services (like Gmail) require you to enable “less secure app access” to allow SMTP connections. Alternatively, use App Passwords for enhanced security.
   • Check your email provider’s settings for specific configurations.
2. Avoid Hardcoding Passwords:
   • Use environment variables or secret management tools to store sensitive credentials.
3. Rate Limits:
   • Be aware of rate limits imposed by email providers to avoid being blocked.

Using SMTP in Python with the smtplib library is a straightforward way to send emails programmatically. By setting up the SMTP server details, creating the email content, and authenticating with the server, you can easily send plain text emails or even emails with attachments. For secure and scalable implementations, always follow best practices for handling sensitive information.