AWS Lambda Receive Email Forward Function

aws_lambda_forward_email_inline.py

from __future__ import print_function
import boto3
import json
import os
import re
from email.parser import Parser
from datetime import datetime
import logging

## Thanks to:
# https://gist.github.com/stenius/c6983f990bbbb1e49e4f
# https://bravokeyl.com/how-to-set-up-email-forwarding-with-amazon-ses/#Create-a-Lambda-function-to-forward-recieved-email
# https://github.com/arithmetric/aws-lambda-ses-forwarder
###
# Dincer Kavraal -- dincer(AT)mctdata.com
###


Log = logging.getLogger()
Log.setLevel(logging.DEBUG)

FORWARD_ADDRESSES = ["to-me@example.com",
		     "to-him-1@example.com",
		     "to-her-2@example.com"]
FROM_ADDRESS = "Sender <example@example.com>"
EMAIL_DOMAIN = "example.com"  # my aws receiver email domain
SPAMMER_DOMAINS = map(re.compile, ["example.com"])
SPAMMER_EMAILS = map(re.compile, ["spammer-jack@example.com"])


RE_DOMAIN = re.compile("\@(.*)$")

def decode_email(msg_str):
	p = Parser()
	message = p.parsestr(msg_str)
	decoded_message = ''
	for part in message.walk():
		charset = part.get_content_charset()
		if part.get_content_type() == 'text/plain':
			part_str = part.get_payload(decode=1)
			decoded_message += part_str.decode(charset)
	return decoded_message
	
def print_with_timestamp(*args):
	print(datetime.utcnow().isoformat(), *args)

def lambda_handler(event, context):
	print_with_timestamp('Starting - inbound-sns-spam-filter')
	
	Log.debug(json.dumps(event, indent=4))

	ses_notification = event['Records'][0]['Sns']
	message_id = ses_notification['MessageId']
	message = json.loads(ses_notification["Message"])
	receipt = message['receipt']
	sender = message['mail']['source']
	subject = message['mail']['commonHeaders']['subject']
	sender_domain = (RE_DOMAIN.findall(sender) or [""])[0]
	
	print_with_timestamp('Processing message:', message_id)

	# Check if any spam check failed
	if (receipt['spfVerdict']['status'] == 'FAIL' or
			receipt['dkimVerdict']['status'] == 'FAIL' or
			receipt['spamVerdict']['status'] == 'FAIL' or
			receipt['virusVerdict']['status'] == 'FAIL' or
			all(map(lambda x: x.search(sender_domain), SPAMMER_DOMAINS)) or
			all(map(lambda x: x.search(sender), SPAMMER_EMAILS))):

		send_bounce_params = {
			'OriginalMessageId': message_id,
			'BounceSender': 'mailer-daemon@{}'.format(EMAIL_DOMAIN),
			'MessageDsn': {
				'ReportingMta': 'dns; {}'.format(EMAIL_DOMAIN),
				'ArrivalDate': datetime.now().isoformat()
			},
			'BouncedRecipientInfoList': []
		}

		for recipient in receipt['recipients']:
			send_bounce_params['BouncedRecipientInfoList'].append({
				'Recipient': recipient,
				'BounceType': 'ContentRejected'
			})

		print_with_timestamp('Bouncing message with parameters:')
		print_with_timestamp(json.dumps(send_bounce_params))

		try:
			ses_client = boto3.client('ses')
			bounceResponse = ses_client.send_bounce(**send_bounce_params)
			print_with_timestamp('Bounce for message ', message_id, ' sent, bounce message ID: ', bounceResponse['MessageId'])
			return {'disposition': 'stop_rule_set'}
		except Exception as e:
			print_with_timestamp(e)
			print_with_timestamp('An error occurred while sending bounce for message: ', message_id)
			raise e
	else:
		print_with_timestamp('Accepting message:', message_id)

	# now distribute to list:
	action = receipt['action']
	if (action['type'] != "S3"):
		Log.exception("Mail body is not saved to S3. Or I have done sth wrong.")
		return None
	
	try:
		ses_client = boto3.client('ses')
		s3_client = boto3.resource('s3')
		mail_obj = s3_client.Object(action['bucketName'], action['objectKey'])
		body = decode_email(mail_obj.get()["Body"].read())
		try:
			response = ses_client.send_email(
				Source=FROM_ADDRESS,
				Destination={
					'ToAddresses': FORWARD_ADDRESSES,
				},  
				Message={
					'Subject': {
						'Data': subject,
					},
					'Body': {
						'Text': {
							'Data': body,
						},
						'Html': {
							'Data': body.replace("\n", "<br />"),
						}
					}
				},  
			)
		except Exception as e1:
			print_with_timestamp(e1)
			print_with_timestamp('An error occurred while sending bounce for message: ', message_id)
			raise e1
	except Exception as e2:
		print_with_timestamp(e2)
		print_with_timestamp('An error occurred while sending bounce for message: ', message_id)
		raise e2

	return None
	
	

Setting_Up_Email_Receiving_in_AWS_Lambda_and_Forwarding.md

Set up an IAM Role called (say) SNSEmailForwarder:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "logs:CreateLogGroup",
                "logs:CreateLogStream",
                "logs:PutLogEvents"
            ],
            "Resource": "arn:aws:logs:*:*:*"
        },
        {
            "Effect": "Allow",
            "Action": [
                "sns:GetTopicAttributes",
                "sns:List*",
                "sns:Publish"
            ],
            "Resource": "*"
        },
        {
            "Effect": "Allow",
            "Action": [
                "ses:SendRawEmail",
                "ses:SendEmail",
                "ses:SendBounce"
            ],
            "Resource": "*"
        },
        {
            "Effect": "Allow",
            "Action": [
                "s3:GetObject",
                "s3:PutObject"
            ],
            "Resource": "arn:aws:s3:::YOUR_S3_BUCKET/*"
        }
    ]
}

Verify your email domain on AWS SES (you can't use sandboxed mail domain, so says AWS) :

1. http://docs.aws.amazon.com/ses/latest/DeveloperGuide/verify-domains.html

Setup an SNS topic:

1. Go to https://console.aws.amazon.com/sns
2. Create topic
3. Topic Name: SNSForwardEmails

Setup a Lambda function: 0) Go to https://console.aws.amazon.com/lambda

1. Create new lambda function
2. Run time: Python 2.7
3. Select blueprint > Blank Function
4. Configure Triggers > Select "SNS" in the gray empty box on left of lambda logo-sign
5. SNS topic: select the topic you have created above. (SNSForwardEmails)
6. Enable Trigger: check the box
7. Create the function
8. Name: LambdaForwardEmails Runtime: Python 2.7 Code entry type: Edit code inline in the text area, copy-paste the whole file I shared here. Role: Choose an existing role Existing Role: the one you have created above. (SNSEmailForwarder)
9. Next > Create Function

Setup SES:

1. Go to https://console.aws.amazon.com/ses
2. Rule Sets (on the left menu)
3. Create a Receipt Rule
4. Rule Set Name: EmailForwardingRules
5. OPTIONAL: enter your domain name without at sign such as: example.com (Add Receipt)
6. Next Step
7. Add Action: S3
8. S3 Bucket: (create sth) Emails Encrypt Message: (uncheck, I am not sure about the consequences of custom encryption) SNS Topic: SNSEmailForwarder (this is important)
9. Create Rule

It seems ok. Test with a real email. (In the Lambda editor) The test scenario AWS provides cannot simulate an email message totally.