AWS EC2 电子邮件转发：使用 Lambda 将传入电子邮件转发到外部目的地

Question

我正在按照 AWS 教程将电子邮件转发到我的 Gmail 帐户，该教程位于此处：https://aws.amazon.com/blogs/messaging-and-targeting/forward-incoming-email-to-an-external-destination/

我已经完成了所有这些工作，但是转发的电子邮件以附件的形式出现，必须下载才能阅读。

我想知道的是如何让这个转发器使电子邮件看起来像普通电子邮件一样。我搜索了 SO，但发现关于该主题的线程很少。因此，我自己研究并弄清楚了，并在下面为其他关注此问题的人提供了答案。

Answer 1

使用以下 Python 代码代替教程中提供的代码。您转发的电子邮件将以您想要的方式到达。

请记住，您的 lambda 函数可以运行多长时间是有时间限制的。解码和编码大型附件需要时间。因此，任何太大的附件（如音频/视频文件）都可能导致整个转发失败。但是，该失败不会阻止 AWS 一次又一次地重试，并且每次尝试都会再次超时。

# Copyright 2010-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
# Altered from original by Adam Winter
#
# This file is licensed under the Apache License, Version 2.0 (the "License").
# You may not use this file except in compliance with the License. A copy of the
# License is located at
#
# http://aws.amazon.com/apache2.0/
#
# This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS
# OF ANY KIND, either express or implied. See the License for the specific
# language governing permissions and limitations under the License.

import os
import boto3
import email
import re
import html
from botocore.exceptions import ClientError
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from email.mime.application import MIMEApplication
from email.mime.image import MIMEImage

region = os.environ['Region']

def get_message_from_s3(message_id):

    incoming_email_bucket = os.environ['MailS3Bucket']
    incoming_email_prefix = os.environ['MailS3Prefix']

    if incoming_email_prefix:
        object_path = (incoming_email_prefix + "/" + message_id)
    else:
        object_path = message_id

    object_http_path = (f"http://s3.console.aws.amazon.com/s3/object/{incoming_email_bucket}/{object_path}?region={region}")

    # Create a new S3 client.
    client_s3 = boto3.client("s3")

    # Get the email object from the S3 bucket.
    object_s3 = client_s3.get_object(Bucket=incoming_email_bucket,
        Key=object_path)
    # Read the content of the message.
    file = object_s3['Body'].read()

    file_dict = {
        "file": file,
        "path": object_http_path
    }

    return file_dict

def create_message(file_dict):

    stringMsg = file_dict['file'].decode('utf-8')

    # Create a MIME container.
    msg = MIMEMultipart('alternative')

    sender = os.environ['MailSender']
    recipient = os.environ['MailRecipient']

    # Parse the email body.
    mailobject = email.message_from_string(file_dict['file'].decode('utf-8'))
    #print(mailobject.as_string())

    # Get original sender for reply-to
    from_original = mailobject['Return-Path']
    from_original = from_original.replace('<', '');
    from_original = from_original.replace('>', '');
    print(from_original)

    # Create a new subject line.
    subject = mailobject['Subject']
    print(subject)

    if mailobject.is_multipart():

        #The quick and dirty way.  If you don't like this, use the for loop below it.
        index = stringMsg.find('Content-Type: multipart/')
        stringBody = stringMsg[index:]
        #print(stringBody)
        stringData = 'Subject: ' + subject + '\nTo: ' + sender + '\nreply-to: ' + from_original + '\n' + stringBody

        message = {
            "Source": sender,
            "Destinations": recipient,
            "Data": stringData
        }
        return message

        for part in mailobject.walk():
            ctype = part.get_content_type()
            cdispo = str(part.get('Content-Disposition'))

            # case for each common content type
            if ctype == 'text/plain' and 'attachment' not in cdispo:
                bodyPart = MIMEText(part.get_payload(decode=True), 'plain', part.get_content_charset())
                msg.attach(bodyPart)

            if ctype == 'text/html' and 'attachment' not in cdispo:
                mt = MIMEText(part.get_payload(decode=True), 'html', part.get_content_charset())
                email.encoders.encode_quopri(mt)
                del mt['Content-Transfer-Encoding']
                mt.add_header('Content-Transfer-Encoding', 'quoted-printable')
                msg.attach(mt)

            if 'attachment' in cdispo and 'image' in ctype:
                mi = MIMEImage(part.get_payload(decode=True), ctype.replace('image/', ''))
                del mi['Content-Type']
                del mi['Content-Disposition']
                mi.add_header('Content-Type', ctype)
                mi.add_header('Content-Disposition', cdispo)
                msg.attach(mi)

            if 'attachment' in cdispo and 'application' in ctype:
                ma = MIMEApplication(part.get_payload(decode=True), ctype.replace('application/', ''))
                del ma['Content-Type']
                del ma['Content-Disposition']
                ma.add_header('Content-Type', ctype)
                ma.add_header('Content-Disposition', cdispo)
                msg.attach(ma)


    # not multipart - i.e. plain text, no attachments, keeping fingers crossed
    else:
        body = MIMEText(mailobject.get_payload(decode=True), 'UTF-8')
        msg.attach(body)

    # The file name to use for the attached message. Uses regex to remove all
    # non-alphanumeric characters, and appends a file extension.
    filename = re.sub('[^0-9a-zA-Z]+', '_', subject_original)

    # Add subject, from and to lines.
    msg['Subject'] = subject
    msg['From'] = sender
    msg['To'] = recipient
    msg['reply-to'] = mailobject['Return-Path']

    # Create a new MIME object.
    att = MIMEApplication(file_dict["file"], filename)
    att.add_header("Content-Disposition", 'attachment', filename=filename)

    # Attach the file object to the message.
    msg.attach(att)
    message = {
        "Source": sender,
        "Destinations": recipient,
        "Data": msg.as_string()
    }
    return message

def send_email(message):
    aws_region = os.environ['Region']
# Create a new SES client.
    client_ses = boto3.client('ses', region)
    # Send the email.
    try:
        #Provide the contents of the email.
        response = client_ses.send_raw_email(
            Source=message['Source'],
            Destinations=[
                message['Destinations']
            ],
            RawMessage={
                'Data':message['Data']
            }
        )

    # Display an error if something goes wrong.
    except ClientError as e:
        print('send email ClientError Exception')
        output = e.response['Error']['Message']
    else:
        output = "Email sent! Message ID: " + response['MessageId']

    return output

def lambda_handler(event, context):
    # Get the unique ID of the message. This corresponds to the name of the file
    # in S3.
    message_id = event['Records'][0]['ses']['mail']['messageId']
    print(f"Received message ID {message_id}")

    # Retrieve the file from the S3 bucket.
    file_dict = get_message_from_s3(message_id)

    # Create the message.
    message = create_message(file_dict)

    # Send the email and print the result.
    result = send_email(message)
    print(result)

Answer 2

你可以无视下面这条消息，我看到你的cmets关于“又快又脏”，让我探索

return message 是错字吗，在这段代码中没有意义吗？

    if mailobject.is_multipart():

        #The quick and dirty way.  If you don't like this, use the for loop below it.
        index = stringMsg.find('Content-Type: multipart/')
        stringBody = stringMsg[index:]
        #print(stringBody)
        stringData = 'Subject: ' + subject + '\nTo: ' + sender + '\nreply-to: ' + from_original + '\n' + stringBody

        message = {
            "Source": sender,
            "Destinations": recipient,
            "Data": stringData
        }
        return message

顺便说一句：感谢您提供此代码 - 我一直在寻找附件示例的替代方法，但不想纠结于您在做什么，所以谢谢！