My emails can be correctly sent but don't show correctly in the receiver mails. It looks like this:
To: =?utf-8?b?..?= <....com> MIME-Version: 1.0 Content-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...
The MIME string is directly shown except the Subject and the From line(It is shown after the To) as well as all bodies in plain text.
There's my code:
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)
And I just do:
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)
I'm the OP of the question. I just solved this problem by myself and I'd share the solution.
TLNR: Non-Ascii chars are used in my mails so use msg = EmailMessage(EmailPolicy(utf8=True)) instead of msg = EmailMessage().
I misunderstood these sentences in the doc of SMTP.send_message:
If any of the addresses in from_addr and to_addrs contain non-ASCII characters and the server does not advertise SMTPUTF8 support, an SMTPNotSupported error is raised. Otherwise the Message is serialized with a clone of its policy with the utf8 attribute set to True, and SMTPUTF8 and BODY=8BITMIME are added to mail_options.
Since I add a non-ASCII header to my address, I believe that smtplib will automatically use the utf8 policy for me. But in the file smtplib.py I saw this:
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
That is, the function only checks if the address parts have non-ASCII chars but not along with the header names.
After that, the message is dealt with as pure ASCII content, that's maybe no problem, I have no idea why, but somohow, many extra /r chars are inserted before and after the To:xxx line, which makes the smtp server think this as a separator maybe? And finally caused the problem.