使用 Python 向 Gmail 发送带有内联图像的电子邮件

Question

我的目标是使用 Python 向具有内嵌图像的 Gmail 用户发送电子邮件。由于图像的敏感性（来自我工作的数据），无法在线托管此图像，然后通过href 链接到它。

我尝试将base64 版本编码为HTML，然后发送HTML，但众所周知这是行不通的。然后我注意到，在 Gmail 中，您可以将图像拖放到发送框中，它将在接收端内联显示。鉴于此，我尝试从 Python 发送一封电子邮件，并将图像作为附件。这在下面的代码中可以看到，但不幸的是图像没有内联显示。

那么我的问题是：如何发送图像以使其内联显示？

import smtplib
from email.MIMEMultipart import MIMEMultipart
from email.MIMEBase import MIMEBase
from email.MIMEText import MIMEText
from email import Encoders
import os

gmail_user = "user1@gmail.com"
gmail_pwd = "pass"

to = "user2@gmail.com"
subject = "Report"
text = "Picture report"
attach = 'TESTING.png'

msg = MIMEMultipart()

msg['From'] = gmail_user
msg['To'] = to
msg['Subject'] = subject

msg.attach(MIMEText(text))

part = MIMEBase('application', 'octet-stream')
part.set_payload(open(attach, 'rb').read())
Encoders.encode_base64(part)
part.add_header('Content-Disposition',
   'attachment; filename="%s"' % os.path.basename(attach))
msg.attach(part)

mailServer = smtplib.SMTP("smtp.gmail.com", 587)
mailServer.ehlo()
mailServer.starttls()
mailServer.ehlo()
mailServer.login(gmail_user, gmail_pwd)
mailServer.sendmail(gmail_user, to, msg.as_string())
# Should be mailServer.quit(), but that crashes...
mailServer.close()

当我手动将内联图像发送给自己时，“原始电子邮件”是这样的：

  Content-Type: multipart/related; boundary=047d7bd761fe73e03304e7e02237

--047d7bd761fe73e03304e7e02237
Content-Type: multipart/alternative; boundary=047d7bd761fe73e03004e7e02236

--047d7bd761fe73e03004e7e02236
Content-Type: text/plain; charset=ISO-8859-1

[image: Inline images 1]

--047d7bd761fe73e03004e7e02236
Content-Type: text/html; charset=ISO-8859-1

<div dir="ltr"><img alt="Inline images 1" src="cid:ii_141810ee4ae92ac6" height="400" width="534"><br></div>

--047d7bd761fe73e03004e7e02236--
--047d7bd761fe73e03304e7e02237
Content-Type: image/png; name="Testing.png"
Content-Transfer-Encoding: base64
Content-ID: <ii_141810ee4ae92ac6>
X-Attachment-Id: ii_141810ee4ae92ac6

当我通过 Python 将它作为附件发送给自己时，情况就大不相同了：

Content-Type: multipart/mixed; boundary="===============6881579935569047077=="
MIME-Version: 1.0
(.... some stuff deleted here)
--===============6881579935569047077==
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit

See attachment for report.
--===============6881579935569047077==
Content-Type: application/octet-stream
MIME-Version: 1.0
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="TESTING.png"

Answer 1

我认为您需要添加以下几行：

from email.mime.image import MIMEImage

body = MIMEText('<p>Test Image<img src="cid:testimage" /></p>', _subtype='html')
msg.attach(body)


img = MIMEImage(image.read(), 'jpeg')
img.add_header('Content-Id', '<testimage>')
msg.attach(img)

testimage 应替换为唯一标识符

Answer 2

似乎遵循 gmail 电子邮件模板有效：

* multipart/alternative
  - text/plain
  - multipart/related
    + text/html
      <img src="cid:msgid"/>
    + image/png
      Content-ID: <msgid>

基于email module docs的示例：

#!/usr/bin/env python3
import html
import mimetypes
from email.headerregistry import Address
from email.message import EmailMessage
from email.utils import make_msgid
from pathlib import Path

title = 'Picture report…'
path = Path('TESTING.png')
me = Address("Pepé Le Pew", *gmail_user.rsplit('@', 1))

msg = EmailMessage()
msg['Subject'] = 'Report…'
msg['From'] = me
msg['To'] = [me]
msg.set_content('[image: {title}]'.format(title=title))  # text/plain
cid = make_msgid()[1:-1]  # strip <>    
msg.add_alternative(  # text/html
    '<img src="cid:{cid}" alt="{alt}"/>'
    .format(cid=cid, alt=html.escape(title, quote=True)),
    subtype='html')
maintype, subtype = mimetypes.guess_type(str(path))[0].split('/', 1)
msg.get_payload()[1].add_related(  # image/png
    path.read_bytes(), maintype, subtype, cid="<{cid}>".format(cid=cid))

# save to disk a local copy of the message
Path('outgoing.msg').write_bytes(bytes(msg))

通过 gmail 发送msg：

import smtplib
import ssl

with smtplib.SMTP('smtp.gmail.com', timeout=10) as s:
    s.starttls(context=ssl.create_default_context())
    s.login(gmail_user, gmail_password)
    s.send_message(msg)

Python 2/3 兼容版本

* multipart/related
  - multipart/alternative
    + text/plain
    + text/html
      <div dir="ltr"><img src="cid:ii_xyz" alt="..."><br></div>
  - image/jpeg
    Content-ID: <ii_xyz>

基于Send an HTML email with embedded image and plain text alternate:

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import cgi
import uuid
import os
from email.mime.multipart import MIMEMultipart
from email.mime.text      import MIMEText
from email.mime.image     import MIMEImage
from email.header         import Header    

img = dict(title=u'Picture report…', path=u'TESTING.png', cid=str(uuid.uuid4()))

msg = MIMEMultipart('related')
msg['Subject'] = Header(u'Report…', 'utf-8')
msg['From'] = gmail_user
msg['To'] = ", ".join([to])
msg_alternative = MIMEMultipart('alternative')
msg.attach(msg_alternative)
msg_text = MIMEText(u'[image: {title}]'.format(**img), 'plain', 'utf-8')
msg_alternative.attach(msg_text)

msg_html = MIMEText(u'<div dir="ltr">'
                     '<img src="cid:{cid}" alt="{alt}"><br></div>'
                    .format(alt=cgi.escape(img['title'], quote=True), **img),
                    'html', 'utf-8')
msg_alternative.attach(msg_html)

with open(img['path'], 'rb') as file:
    msg_image = MIMEImage(file.read(), name=os.path.basename(img['path']))
    msg.attach(msg_image)
msg_image.add_header('Content-ID', '<{}>'.format(img['cid']))

通过 gmail 发送msg：

import ssl

s = SMTP_SSL('smtp.gmail.com', timeout=10,
             ssl_kwargs=dict(cert_reqs=ssl.CERT_REQUIRED,
                             ssl_version=ssl.PROTOCOL_TLSv1,
                             # http://curl.haxx.se/ca/cacert.pem
                             ca_certs='cacert.pem')) 
s.set_debuglevel(0)
try:
    s.login(gmail_user, gmail_pwd)
    s.sendmail(msg['From'], [to], msg.as_string())
finally:
    s.quit()

SMTP_SSL 是可选的，您可以使用问题中的starttls 方法：

import smtplib
import socket
import ssl
import sys

class SMTP_SSL(smtplib.SMTP_SSL):
    """Add support for additional ssl options."""
    def __init__(self, host, port=0, **kwargs):
        self.ssl_kwargs = kwargs.pop('ssl_kwargs', {})
        self.ssl_kwargs['keyfile'] = kwargs.pop('keyfile', None)
        self.ssl_kwargs['certfile'] = kwargs.pop('certfile', None)
        smtplib.SMTP_SSL.__init__(self, host, port, **kwargs)

    def _get_socket(self, host, port, timeout):
        if self.debuglevel > 0:
            print>>sys.stderr, 'connect:', (host, port)
        new_socket = socket.create_connection((host, port), timeout)
        new_socket = ssl.wrap_socket(new_socket, **self.ssl_kwargs)
        self.file = getattr(smtplib, 'SSLFakeFile', lambda x: None)(new_socket)
        return new_socket