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Sending Email Using SMTP in Python

Python provides a built-in library called smtplib to send emails using the Simple Mail Transfer Protocol (SMTP). With this library, you can connect to an email server, authenticate, and send emails programmatically.

This guide will walk you through the steps to send emails using Python.

Steps to Send Email Using SMTP

  1. Set Up SMTP Server: Connect to the email provider’s SMTP server (e.g., Gmail, Yahoo).
  2. Authenticate: Log in using your email and password (use app-specific passwords or OAuth for added security).
  3. Compose the Email: Define the sender, recipient(s), subject, and message body.
  4. Send the Email: Use the smtplib library to send the email.

Code Example: Sending a Simple Email

Here’s a basic example of sending an email using Python.

Code:


import smtplib
from email.mime.text import MIMEText

# Email configuration
SMTP_SERVER = "smtp.gmail.com"
SMTP_PORT = 587
EMAIL = "your_email@gmail.com"  # Your email address
PASSWORD = "your_password"      # Your email password (use app-specific password for Gmail)

# Create the email
subject = "Test Email"
body = "Hello! This is a test email sent from Python."
recipient = "recipient_email@gmail.com"

# Format the email
message = MIMEText(body, "plain")
message["Subject"] = subject
message["From"] = EMAIL
message["To"] = recipient

try:
    # Connect to the SMTP server
    with smtplib.SMTP(SMTP_SERVER, SMTP_PORT) as server:
        server.starttls()  # Start TLS (Transport Layer Security) encryption
        server.login(EMAIL, PASSWORD)  # Log in to the email account
        server.send_message(message)  # Send the email
        print("Email sent successfully!")

except Exception as e:
    print(f"Error: {e}")

Breaking Down the Code

  1. SMTP Configuration:

    • SMTP_SERVER: The SMTP server address (e.g., smtp.gmail.com for Gmail).
    • SMTP_PORT: The port number (usually 587 for TLS or 465 for SSL).

  2. Authentication:

    • Use your email and password. For Gmail, enable “Allow less secure apps” or generate an app-specific password.

  3. Message Formatting:

    • MIMEText: Creates a plain text email body. You can also use MIMEText(body, "html") for HTML emails.

  4. TLS Encryption:

    • starttls(): Secures the connection by encrypting the communication with the server.

  5. Send the Email:

    • server.send_message(message): Sends the email to the specified recipient(s).

Sending HTML Emails

To send an email with HTML content, change the email body type to "html".

Example: HTML Email


from email.mime.text import MIMEText

# Email content
html_body = """
<html>
    <body>
        <h1>Hello!</h1>
        <p>This is an <b>HTML email</b> sent from Python.</p>
    </body>
</html>
"""

message = MIMEText(html_body, "html")
message["Subject"] = "HTML Email Test"
message["From"] = EMAIL
message["To"] = recipient

Sending Emails with Attachments

To send emails with attachments, you need to use the MIMEMultipart class.

Example: Email with Attachment


import smtplib
from email.mime.text import MIMEText
from email.mime.multipart import MIMEMultipart
from email.mime.base import MIMEBase
from email import encoders

# Email configuration
SMTP_SERVER = "smtp.gmail.com"
SMTP_PORT = 587
EMAIL = "your_email@gmail.com"
PASSWORD = "your_password"

# Create the email
subject = "Email with Attachment"
body = "This email contains an attachment."

message = MIMEMultipart()
message["Subject"] = subject
message["From"] = EMAIL
message["To"] = recipient

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

# Attach a file
filename = "example.txt"  # File to attach
with open(filename, "rb") as attachment:
    part = MIMEBase("application", "octet-stream")
    part.set_payload(attachment.read())

# Encode the file in base64
encoders.encode_base64(part)
part.add_header(
    "Content-Disposition",
    f"attachment; filename={filename}"
)
message.attach(part)

# Send the email
try:
    with smtplib.SMTP(SMTP_SERVER, SMTP_PORT) as server:
        server.starttls()
        server.login(EMAIL, PASSWORD)
        server.send_message(message)
        print("Email with attachment sent successfully!")
except Exception as e:
    print(f"Error: {e}")

Common SMTP Server Settings

Provider SMTP Server Port (TLS) Port (SSL)
Gmail smtp.gmail.com 587 465
Yahoo Mail smtp.mail.yahoo.com 587 465
Outlook smtp.office365.com 587 –

Security Considerations

  1. App-Specific Passwords: For Gmail and some other providers, use an app-specific password instead of your main password.

  2. Environment Variables: Store sensitive information like email credentials in environment variables or configuration files instead of hardcoding them.

  3. OAuth2 Authentication: For enhanced security, consider using OAuth2 for authenticating with email providers.

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