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Sending Email with SMTP ​

SMTP is the protocol used to send emails, and Python provides built-in support through the smtplib and email modules. The email module constructs the emails, while smtplib handles the sending.

Sending a Simple Text Email ​

To create a simple plain text email:

python
from email.mime.text import MIMEText

msg = MIMEText('hello, send by Python...', 'plain', 'utf-8')

Next, send the email:

python
import smtplib

from_addr = input('From: ')
password = input('Password: ')
to_addr = input('To: ')
smtp_server = input('SMTP server: ')

server = smtplib.SMTP(smtp_server, 25)
server.set_debuglevel(1)
server.login(from_addr, password)
server.sendmail(from_addr, [to_addr], msg.as_string())
server.quit()

Adding Email Headers ​

To ensure a complete email, add headers like From, To, and Subject:

python
from email import encoders
from email.header import Header
from email.utils import parseaddr, formataddr

def _format_addr(s):
    name, addr = parseaddr(s)
    return formataddr((Header(name, 'utf-8').encode(), addr))

msg['From'] = _format_addr('Python Lover <%s>' % from_addr)
msg['To'] = _format_addr('Admin <%s>' % to_addr)
msg['Subject'] = Header('Greetings from SMTP...', 'utf-8').encode()

Sending HTML Emails ​

To send an HTML email, simply change the MIME type:

python
msg = MIMEText('<html><body><h1>Hello</h1><p>send by <a href="http://www.python.org">Python</a>...</p></body></html>', 'html', 'utf-8')

Sending Emails with Attachments ​

To include attachments, use MIMEMultipart:

python
from email.mime.multipart import MIMEMultipart
from email.mime.base import MIMEBase

msg = MIMEMultipart()
msg['From'] = _format_addr('Python Lover <%s>' % from_addr)
msg['To'] = _format_addr('Admin <%s>' % to_addr)
msg['Subject'] = Header('Greetings with Attachment...', 'utf-8').encode()

msg.attach(MIMEText('send with file...', 'plain', 'utf-8'))

with open('path/to/file.png', 'rb') as f:
    mime = MIMEBase('image', 'png', filename='file.png')
    mime.add_header('Content-Disposition', 'attachment', filename='file.png')
    mime.set_payload(f.read())
    encoders.encode_base64(mime)
    msg.attach(mime)

Sending Embedded Images ​

To embed images in HTML emails, reference them using cid:

python
msg.attach(MIMEText('<html><body><h1>Hello</h1><p><img src="cid:0"></p></body></html>', 'html', 'utf-8'))

Supporting Both HTML and Plain Text ​

Use MIMEMultipart('alternative') to send both formats:

python
msg = MIMEMultipart('alternative')
msg.attach(MIMEText('hello', 'plain', 'utf-8'))
msg.attach(MIMEText('<html><body><h1>Hello</h1></body></html>', 'html', 'utf-8'))

Using Secure SMTP ​

For secure connections, such as with Gmail, use port 587 and start TLS:

python
smtp_server = 'smtp.gmail.com'
smtp_port = 587
server = smtplib.SMTP(smtp_server, smtp_port)
server.starttls()

Summary ​

Python's smtplib makes sending emails straightforward. By mastering the construction of various email types and correctly setting headers, you can send complex emails with ease. Explore the email.mime documentation for detailed usage and capabilities.