mirror of
https://github.com/simple-login/app.git
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289 lines
9.2 KiB
Python
289 lines
9.2 KiB
Python
"""
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Handle the email *forward* and *reply*. phase. There are 3 actors:
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- website: who sends emails to alias@sl.co address
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- SL email handler (this script)
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- user personal email: to be protected. Should never leak to website.
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This script makes sure that in the forward phase, the email that is forwarded to user personal email has the following
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envelope and header fields:
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Envelope:
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mail from: @website
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rcpt to: @personal_email
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Header:
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From: @website
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To: alias@sl.co # so user knows this email is sent to alias
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Reply-to: special@sl.co # magic HERE
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And in the reply phase:
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Envelope:
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mail from: @website
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rcpt to: @website
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Header:
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From: alias@sl.co # so for website the email comes from alias. magic HERE
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To: @website
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The special@sl.co allows to hide user personal email when user clicks "Reply" to the forwarded email.
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It should contain the following info:
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- alias
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- @website
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"""
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import time
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from email.message import EmailMessage
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from email.parser import Parser
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from email.policy import SMTPUTF8
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from smtplib import SMTP
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from aiosmtpd.controller import Controller
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from app.config import EMAIL_DOMAIN, POSTFIX_SERVER, URL
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from app.extensions import db
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from app.log import LOG
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from app.models import GenEmail, ForwardEmail, ForwardEmailLog
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from app.utils import random_words
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from server import create_app
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# fix the database connection leak issue
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# use this method instead of create_app
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def new_app():
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app = create_app()
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@app.teardown_appcontext
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def shutdown_session(response_or_exc):
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# same as shutdown_session() in flask-sqlalchemy but this is not enough
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db.session.remove()
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# dispose the engine too
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db.engine.dispose()
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return app
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class MailHandler:
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async def handle_DATA(self, server, session, envelope):
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LOG.debug(">>> New message <<<")
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LOG.debug("Mail from %s", envelope.mail_from)
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LOG.debug("Rcpt to %s", envelope.rcpt_tos)
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message_data = envelope.content.decode("utf8", errors="replace")
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# Only when debug
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# LOG.debug("Message data:\n")
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# LOG.debug(message_data)
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# host IP, setup via Docker network
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smtp = SMTP(POSTFIX_SERVER, 25)
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msg = Parser(policy=SMTPUTF8).parsestr(message_data)
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if not envelope.rcpt_tos[0].startswith("reply+"): # Forward case
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LOG.debug("Forward phase")
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app = new_app()
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with app.app_context():
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return self.handle_forward(envelope, smtp, msg)
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else:
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LOG.debug("Reply phase")
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app = new_app()
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with app.app_context():
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return self.handle_reply(envelope, smtp, msg)
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def handle_forward(self, envelope, smtp, msg: EmailMessage) -> str:
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"""return *status_code message*"""
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alias = envelope.rcpt_tos[0] # alias@SL
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gen_email = GenEmail.get_by(email=alias)
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if not gen_email:
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LOG.d("alias %s not exist")
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return "510 Email not exist"
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user_email = gen_email.user.email
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website_email = get_email_part(msg["From"])
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forward_email = ForwardEmail.get_by(
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gen_email_id=gen_email.id, website_email=website_email
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)
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if not forward_email:
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LOG.debug(
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"create forward email for alias %s and website email %s",
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alias,
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website_email,
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)
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# todo: make sure reply_email is unique
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reply_email = f"reply+{random_words()}@{EMAIL_DOMAIN}"
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forward_email = ForwardEmail.create(
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gen_email_id=gen_email.id,
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website_email=website_email,
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website_from=msg["From"],
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reply_email=reply_email,
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)
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db.session.commit()
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forward_log = ForwardEmailLog.create(forward_id=forward_email.id)
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if gen_email.enabled:
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# add custom header
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add_or_replace_header(msg, "X-SimpleLogin-Type", "Forward")
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# remove reply-to header if present
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if msg["Reply-To"]:
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LOG.d("Delete reply-to header %s", msg["Reply-To"])
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del msg["Reply-To"]
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# change the from header so the sender comes from @SL
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# so it can pass DMARC check
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# replace the email part in from: header
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from_header = (
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get_email_name(msg["From"])
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+ " - "
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+ website_email.replace("@", " at ")
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+ f" <{forward_email.reply_email}>"
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)
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msg.replace_header("From", from_header)
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LOG.d("new from header:%s", from_header)
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# add List-Unsubscribe header
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unsubscribe_link = f"{URL}/dashboard/unsubscribe/{gen_email.id}"
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add_or_replace_header(msg, "List-Unsubscribe", f"<{unsubscribe_link}>")
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add_or_replace_header(
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msg, "List-Unsubscribe-Post", "List-Unsubscribe=One-Click"
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)
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# remove DKIM-Signature as Postfix will add this header
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if msg["DKIM-Signature"]:
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LOG.d("Remove DKIM-Signature %s", msg["DKIM-Signature"])
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del msg["DKIM-Signature"]
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original_subject = msg["Subject"]
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LOG.d(
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"Forward mail from %s to %s, subject %s, mail_options %s, rcpt_options %s ",
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website_email,
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user_email,
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original_subject,
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envelope.mail_options,
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envelope.rcpt_options,
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)
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# smtp.send_message has UnicodeEncodeErroremail issue
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# encode message raw directly instead
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msg_raw = msg.as_string().encode()
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smtp.sendmail(
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forward_email.reply_email,
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user_email,
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msg_raw,
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envelope.mail_options,
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envelope.rcpt_options,
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)
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# smtp.send_message(
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# msg,
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# from_addr=forward_email.reply_email,
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# to_addrs=[user_email], # user personal email
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# mail_options=envelope.mail_options,
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# rcpt_options=envelope.rcpt_options,
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# )
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else:
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LOG.d("%s is disabled, do not forward", gen_email)
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forward_log.blocked = True
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db.session.commit()
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return "250 Message accepted for delivery"
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def handle_reply(self, envelope, smtp, msg: EmailMessage) -> str:
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reply_email = envelope.rcpt_tos[0]
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# reply_email must end with EMAIL_DOMAIN
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if not reply_email.endswith(EMAIL_DOMAIN):
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LOG.error(f"Reply email {reply_email} has wrong domain")
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return "550 wrong reply email"
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forward_email = ForwardEmail.get_by(reply_email=reply_email)
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alias: str = forward_email.gen_email.email
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# todo: add DKIM-Signature for custom domain
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# remove DKIM-Signature for custom domain
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if not alias.endswith(EMAIL_DOMAIN) and msg["DKIM-Signature"]:
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LOG.d(
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"Remove DKIM-Signature %s for custom-domain alias %s",
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msg["DKIM-Signature"],
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alias,
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)
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del msg["DKIM-Signature"]
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# email seems to come from alias
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msg.replace_header("From", alias)
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msg.replace_header("To", forward_email.website_email)
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# add List-Unsubscribe header
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unsubscribe_link = f"{URL}/dashboard/unsubscribe/{forward_email.gen_email_id}"
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add_or_replace_header(msg, "List-Unsubscribe", f"<{unsubscribe_link}>")
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add_or_replace_header(
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msg, "List-Unsubscribe-Post", "List-Unsubscribe=One-Click"
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)
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LOG.d(
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"send email from %s to %s, mail_options:%s,rcpt_options:%s",
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alias,
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forward_email.website_email,
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envelope.mail_options,
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envelope.rcpt_options,
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)
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msg_raw = msg.as_string().encode()
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smtp.sendmail(
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alias,
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forward_email.website_email,
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msg_raw,
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envelope.mail_options,
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envelope.rcpt_options,
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)
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ForwardEmailLog.create(forward_id=forward_email.id, is_reply=True)
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db.session.commit()
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return "250 Message accepted for delivery"
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def add_or_replace_header(msg: EmailMessage, header: str, value: str):
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try:
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msg.add_header(header, value)
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except ValueError:
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# the header exists already
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msg.replace_header(header, value)
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def get_email_name(email_from):
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"""parse email from header and return the name part
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First Last <ab@cd.com> -> First Last
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ab@cd.com -> ""
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"""
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if "<" in email_from:
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return email_from[: email_from.find("<")].strip()
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return ""
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def get_email_part(email_from):
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"""parse email from header and return the email part
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First Last <ab@cd.com> -> ab@cd.com
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ab@cd.com -> ""
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"""
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if "<" in email_from:
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return email_from[email_from.find("<") + 1 : email_from.find(">")].strip()
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return email_from
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if __name__ == "__main__":
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controller = Controller(MailHandler(), hostname="0.0.0.0", port=20381)
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controller.start()
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LOG.d("Start mail controller %s %s", controller.hostname, controller.port)
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while True:
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time.sleep(2)
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