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How to send email with file attachment via SMTP in Python

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This example shows how to send an email with an attachment in Python, with the attachment being read from a file from the filesystem:

send_email_attachment.py
#!/usr/bin/env python3
import smtplib
import mimetypes
from email.message import EmailMessage

# Create message and set text content
msg = EmailMessage()
msg['Subject'] = 'This email contains an attachment'
msg['From'] = 'sender@domain.com'
msg['To'] = 'recipient@domain.com'
# Set text content
msg.set_content('Please see attached file')

def attach_file_to_email(email, filename):
    """Attach a file identified by filename, to an email message"""
    with open(filename, 'rb') as fp:
        file_data = fp.read()
        maintype, _, subtype = (mimetypes.guess_type(filename)[0] or 'application/octet-stream').partition("/")
        email.add_attachment(file_data, maintype=maintype, subtype=subtype, filename=filename)

# Attach files
attach_file_to_email(msg, "myfile.pdf")

def send_mail_smtp(mail, host, username, password):
    s = smtplib.SMTP(host)
    s.starttls()
    s.login(username, password)
    s.send_message(mail)
    s.quit()

send_mail_smtp(msg, 'smtp.my-domain.com', 'sender@domain.com', 'sae7ooka0S')

The utility functions in this code are:

email_utils.py
import smtplib
import mimetypes

def attach_file_to_email(email, filename):
    """Attach a file identified by filename, to an email message"""
    with open(filename, 'rb') as fp:
        file_data = fp.read()
        maintype, _, subtype = (mimetypes.guess_type(filename)[0] or 'application/octet-stream').partition("/")
        email.add_attachment(file_data, maintype=maintype, subtype=subtype, filename=filename)

def send_mail_smtp(mail, host, username, password):
    s = smtplib.SMTP(host)
    s.starttls()
    s.login(username, password)
    s.send_message(mail)
    s.quit()

Initialize your email like this:

create_email_msg.py
# Create message and set text content
msg = EmailMessage()
msg['Subject'] = 'This email contains an attachment'
msg['From'] = 'sender@domain.com'
msg['To'] = 'recipient@domain.com'
# Set text content
msg.set_content('Please see attached file')

and then attach the file like this:

attach_example.py
attach_file_to_email(msg, "myfile.pdf")

and send the email using

send_email_example.py
send_mail_smtp(msg, 'smtp.my-domain.com', 'sender@domain.com', 'sae7ooka0S')
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