python - 使用 Python 将电子邮件发送到带有内联图像的 Gmail

Question

我的目标是使用 Python 向具有内联图像的 Gmail 用户发送电子邮件。由于图像的敏感性(来 self 的工作的数据)，不可能在线托管此图像然后通过 href 链接到它。

我试过将 base64 版本编码成 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，它会在接收端内联显示。鉴于此，我随后尝试从 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显示内联。

那么我的问题是:如何发送图像以内联显示？

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，这就是“原始电子邮件”的样子:

  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

似乎遵循 gmail 电子邮件模板是可行的:

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

基于 email module docs 中的示例:

#!/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