python - 在使用 python 的电子邮件和 smtplib 包发送的电子邮件中，EmailMessage 无法正确显示

Question

我的电子邮件可以正确发送，但在接收方邮件中显示不正确。它看起来像这样:

To: =?utf-8?b?..?= <....com> MIME-Version: 1.0Content-Type: multipart/mixed;boundary="===============5404281335870522242=="

--===============5404281335870522242== Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64

5bCK5pWs55qE5a2U6LaF5YW...

--===============5404281335870522242== Content-Type: image/png Content-Transfer-Encoding: base64 Content-Disposition: attachment;filename="user.png" MIME-Version: 1.0

iVBORw0KGgo...

除了 Subject 外，直接显示 MIME 字符串和 From行(显示在 To 之后)以及纯文本中的所有正文。
这是我的代码:

import smtplib
import ssl
import mimetypes
from pathlib import Path
from email.message import EmailMessage
from email.utils import formataddr
import time

class EmailSender:
    PORT = 465
    CONTEXT = ssl.create_default_context()

    def __init__(
        self,
        username,
        password,
        host,
    ):
        self.username = username
        self.password = password
        self.host = host
        self.mails = []

    def _add_name_header(self, name="", mail_addr=""):
        if name:
            return formataddr((name, mail_addr))
        else:
            return mail_addr

    def add_mail(
        self,
        from_email="",
        from_name="",
        to_email="",
        to_name="",
        subject="",
        message_txt="",
        files=None,
    ):
        msg = EmailMessage()
        msg["Subject"] = subject
        msg["From"] = self._add_name_header(from_name, from_email)
        msg["To"] = self._add_name_header(to_name, to_email)
        msg.set_content(message_txt)

        if not files is None:
            for file_obj in files:
                if file_obj.exists():
                    file = str(file_obj)
                    ctype, encoding = mimetypes.guess_type(file)
                    if ctype is None or encoding is not None:
                        # No guess could be made, or the file is encoded (compressed), so use a generic bag-of-bits type.
                        ctype = "application/octet-stream"
                    maintype, subtype = ctype.split("/", 1)
                    with file_obj.open("rb") as fp:
                        msg.add_attachment(
                            fp.read(),
                            maintype=maintype,
                            subtype=subtype,
                            filename=file_obj.name,
                        )

        self.mails.append(msg)

    def send(self, time_interval=1):
        with smtplib.SMTP_SSL(
            host=self.host, port=self.PORT, context=self.CONTEXT
        ) as server:
            try:
                server.login(user=self.username, password=self.password)
            except Exception as e:
                # Need process errors
                raise e
            for msg in self.mails:
                server.send_message(msg)
                time.sleep(time_interval)

我只是这样做:

sender = EmailSender(
        username, password, host="smtp.163.com"
)

files = list(Path("D:/").glob("*.pdf"))

sender.add_mail(
        from_email, from_name, to_email, to_name, subject, message_txt, files=None
)
sender.send(time_interval=10)

Answer 1

我是问题的 OP。我只是自己解决了这个问题，我会分享解决方案。
TLNR:我的邮件中使用了非 Ascii 字符，因此请使用 msg = EmailMessage(EmailPolicy(utf8=True))而不是 msg = EmailMessage() .
我在 SMTP.send_message 的文档中误解了这些句子:

If any of the addresses in from_addr and to_addrs contain non-ASCIIcharacters and the server does not advertise SMTPUTF8 support, anSMTPNotSupported error is raised. Otherwise the Message is serializedwith a clone of its policy with the utf8 attribute set to True, andSMTPUTF8 and BODY=8BITMIME are added to mail_options.

由于我在地址中添加了非 ASCII header ，因此我相信 smtplib将自动为我使用 utf8 策略。但是在文件 smtplib.py我看见了这个:

if from_addr is None:
    # Some code
    from_addr = email.utils.getaddresses([from_addr])[0][1]
if to_addrs is None:
    # Some code
    to_addrs = [a[1] for a in email.utils.getaddresses(addr_fields)]
# Some code
international = False
try:
    "".join([from_addr, *to_addrs]).encode("ascii")
except UnicodeEncodeError:
    # Some code
    international = True

也就是说，该函数仅检查地址部分是否具有非 ASCII 字符，但不检查标题名称。
之后，消息作为纯ASCII内容处理，这可能没问题，我不知道为什么，但是somohow， 许多额外/r在 To:xxx 前后插入字符线路 , 这让 smtp 服务器认为这是一个分隔符吗？并最终导致了问题。