How to Send Emails with Attachments by SMTP? - Direct Mail

Sending emails with attachments using SMTP requires you to build emails in MIME format.

MIME basic

MIME(Multipurpose Internet Mail Extensions).
RFC, click here.

Note

The total size of the attachment should not exceed 15MB, with a maximum of 100 attachments at a time.

15MB indicates the total size of an email sent by SMTP. Because the base64 encoded email code expands by more than 1.5 times, the total size is not the size seen on the client side. It is recommended to set the attachment limit to 8MB. If you need to send large attachments, it is recommended to add hyperlinks to the content.

Example (python 2.7)

# -*- coding:utf-8 -*-

import urllib, urllib2
import smtplib
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from email.mime.application import MIMEApplication

# Sender address, created in the console
username = 'xxx@xxx.com'
# Sender password, created in the console
password = 'XXXXXXXX'

# Recipient address list, supports up to 30 recipients
rcptlist = ['to1@to.com', 'to2@to.com']
receivers = ','.join(rcptlist)

# Build multipart mail message
msg = MIMEMultipart('mixed')
msg['Subject'] = 'Test Email'
msg['From'] = username
msg['To'] = receivers

# Build text/plain part of multipart/alternative
alternative = MIMEMultipart('alternative')
textplain = MIMEText ('plain text part')
alternative.attach(textplain)

# Build text/html part of multipart/alternative
textplain = MIMEText ('hyper text part')
alternative.attach(texthtml)

# Add alternative into mixed
msg.attach(alternative)

# Attachment type
# xlsx type attachment
xlsxpart = MIMEApplication(open('1.xlsx', 'rb').read())
xlsxpart.add_header('Content-Disposition', 'attachment', filename='1.xlsx')
msg.attach(xlsxpart)

# jpg type attachment
jpgpart = MIMEApplication(open('2.jpg', 'rb').read())
jpgpart.add_header('Content-Disposition', 'attachment', filename='2.jpg')
msg.attach(jpgpart)

# mp3 type attachment
mp3part = MIMEApplication(open('3.mp3', 'rb').read())
mp3part.add_header('Content-Disposition', 'attachment', filename='3.mp3')
msg.attach(mp3part)

# Send mail
try:
    client = smtplib.SMTP()
    # SSL may be needed to create a client in python 2.7 or later
    #client = smtplib.SMTP_SSL()

    client.connect('smtpdm.aliyun.com')
    client.login(username, password)
    # Sender has to match the authorized address
    client.sendmail(username, rcptlist, msg.as_string())
    client.quit()
    Print 'Email delivered successfully!'
except smtplib.SMTPRecipientsRefused:
    Print 'Email delivery failed, invalid recipient'
except smtplib.SMTPAuthenticationError:
    Print 'Email delivery failed, authorization error'
except smtplib.SMTPSenderRefused:
    Print 'Email delivery failed, invalid sender'
except smtplib.SMTPException,e:
    Print 'Email delivery failed, ' e.message

Other example code reference: