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Andreas Knuth 2025-08-31 16:11:14 -05:00
parent 31aea63c61
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# lambda_andreasknuth.py
import os
import boto3
import smtplib
import time
import traceback
from email.parser import BytesParser
from email.policy import default
from email.utils import getaddresses
s3 = boto3.client('s3')
# Environment variables (set these in the Lambda config)
SMTP_HOST = os.environ.get('MAILCOW_SMTP_HOST', 'mail.email-srvr.com')
SMTP_PORT = int(os.environ.get('MAILCOW_SMTP_PORT', '2525')) # default to your mapped port
SMTP_USER = os.environ.get('SMTP_USER') or os.environ.get('MAILCOW_SMTP_USER')
SMTP_PASS = os.environ.get('SMTP_PASS') or os.environ.get('MAILCOW_SMTP_PASS')
# Metadata key/value to mark processed objects (only set when at least one recipient delivered)
PROCESSED_META_KEY = os.environ.get('PROCESSED_META_KEY', 'processed')
PROCESSED_META_VALUE = os.environ.get('PROCESSED_META_VALUE', 'true')
def domain_to_bucket(domain: str) -> str:
return domain.replace('.', '-') + '-emails'
def bucket_to_domain(bucket: str) -> str:
return bucket.replace('-emails', '').replace('-', '.')
def parse_raw_message(raw_bytes: bytes):
try:
parsed = BytesParser(policy=default).parsebytes(raw_bytes)
except Exception:
parsed = None
return parsed
def mark_object_processed(bucket: str, key: str):
try:
head = s3.head_object(Bucket=bucket, Key=key)
current_metadata = head.get('Metadata', {}) or {}
if current_metadata.get(PROCESSED_META_KEY) == PROCESSED_META_VALUE:
print(f"Object {key} in {bucket} already marked processed.")
return
new_meta = current_metadata.copy()
new_meta[PROCESSED_META_KEY] = PROCESSED_META_VALUE
# Copy object onto itself replacing metadata
s3.copy_object(
Bucket=bucket,
Key=key,
CopySource={'Bucket': bucket, 'Key': key},
Metadata=new_meta,
MetadataDirective='REPLACE'
)
print(f"Marked {bucket}/{key} as processed.")
except Exception as e:
print("Failed to mark processed metadata:", e)
traceback.print_exc()
def lambda_handler(event, context):
print("Event:", event)
ses = None
try:
rec = event['Records'][0]
except Exception as e:
print("No Records in event:", e)
return {'statusCode': 400, 'body': 'No Records'}
# Determine bucket/key and initial recipients list
recipients = []
bucket = None
key = None
if 'ses' in rec:
ses = rec['ses']
msg_id = ses['mail']['messageId']
recipients = ses['receipt'].get('recipients', [])
# assume first recipient domain maps to bucket
if recipients:
domain = recipients[0].split('@', 1)[1]
bucket = domain_to_bucket(domain)
prefix = f"emails/{msg_id}"
print(f"SES event: domain={domain}, bucket={bucket}, prefix={prefix}")
resp_list = s3.list_objects_v2(Bucket=bucket, Prefix=prefix)
if 'Contents' not in resp_list or not resp_list['Contents']:
raise Exception(f"No S3 object under {prefix} in {bucket}")
key = resp_list['Contents'][0]['Key']
else:
raise Exception("SES event but no recipients found")
elif 's3' in rec:
s3info = rec['s3']
bucket = s3info['bucket']['name']
key = s3info['object']['key']
print(f"S3 event: bucket={bucket}, key={key}")
# recipients will be parsed from message headers below
else:
raise Exception("Unknown event type")
# Check if already processed (only to avoid unnecessary work; we still honor processed semantics)
try:
head = s3.head_object(Bucket=bucket, Key=key)
if head.get('Metadata', {}).get(PROCESSED_META_KEY) == PROCESSED_META_VALUE:
print(f"Object {key} in {bucket} already processed. Exiting.")
return {'statusCode': 200, 'body': 'already processed'}
except Exception as e:
# If head_object fails, continue and try to process (log for debugging)
print("head_object error (continuing):", e)
# Get raw mail bytes
resp = s3.get_object(Bucket=bucket, Key=key)
raw_bytes = resp['Body'].read()
print(f"Loaded {len(raw_bytes)} bytes from s3://{bucket}/{key}")
parsed = parse_raw_message(raw_bytes)
subj = parsed.get('subject', '(no subject)') if parsed else '(no subject)'
frm_addr = None
if parsed:
from_addrs = getaddresses(parsed.get_all('from', []) or [])
frm_addr = from_addrs[0][1] if from_addrs else None
if not frm_addr:
# fallback: try envelope sender if present in SES event
frm_addr = (ses['mail'].get('source') if ses else None) or ('noreply@' + (bucket_to_domain(bucket) if bucket else 'localhost'))
print(f"From: {frm_addr}, Subject: {subj}")
# If recipients were not provided (S3 path), extract from headers
if not recipients:
if parsed:
to_addrs = [addr for _n, addr in getaddresses(parsed.get_all('to', []) or [])]
cc_addrs = [addr for _n, addr in getaddresses(parsed.get_all('cc', []) or [])]
bcc_addrs = [addr for _n, addr in getaddresses(parsed.get_all('bcc', []) or [])]
recipients = to_addrs + cc_addrs + bcc_addrs
print("Recipients from headers:", recipients)
# filter recipients to bucket domain (safety)
expected_domain = bucket_to_domain(bucket)
recipients = [r for r in recipients if r.lower().split('@')[-1] == expected_domain]
print(f"Recipients after domain filter ({expected_domain}): {recipients}")
else:
print("No parsed headers and no recipients provided; nothing to do.")
recipients = []
# If after all we have no recipients, skip SMTP
delivered = []
refused = {}
if recipients:
# Prepare message string for sendmail (decode bytes safely)
try:
raw_message = raw_bytes.decode('utf-8')
except Exception:
raw_message = raw_bytes.decode('utf-8', errors='replace')
# Determine a sensible local hostname (HELO). Prefer explicit ENV, else use domain of bucket (recipient domain).
env_local = os.environ.get('SMTP_LOCAL_HOSTNAME')
derived_local = bucket_to_domain(bucket) if bucket else None
local_helo = env_local or derived_local or 'localhost'
print(f"Attempting SMTP send to {len(recipients)} recipients via {SMTP_HOST}:{SMTP_PORT} with local_hostname={local_helo}")
start = time.time()
try:
# Pass local_hostname so the server receives a proper FQDN in HELO/EHLO
with smtplib.SMTP(SMTP_HOST, SMTP_PORT, timeout=30, local_hostname=local_helo) as smtp:
smtp.ehlo()
# Try STARTTLS; if it fails, continue (server might be implicit TLS port)
try:
smtp.starttls()
smtp.ehlo()
except Exception as e:
print("STARTTLS not available or failed (continuing):", e)
if SMTP_USER and SMTP_PASS:
try:
smtp.login(SMTP_USER, SMTP_PASS)
except Exception as e:
print("SMTP login failed (continuing):", e)
try:
send_result = smtp.sendmail(frm_addr, recipients, raw_message)
# sendmail returns dict of refused recipients
if isinstance(send_result, dict):
refused = send_result
delivered = [r for r in recipients if r not in refused]
else:
# Unexpected but treat all as delivered
delivered = recipients[:]
refused = {}
except smtplib.SMTPRecipientsRefused as e:
print("SMTPRecipientsRefused:", e)
try:
refused = e.recipients
except Exception:
refused = {r: ('550', 'Recipient refused') for r in recipients}
delivered = [r for r in recipients if r not in refused]
except Exception as e:
print("SMTP sendmail error:", e)
refused = {r: ('error', str(e)) for r in recipients}
delivered = []
except Exception as e:
print("Error connecting to SMTP host:", e)
refused = {r: ('connect-error', str(e)) for r in recipients}
delivered = []
print(f"SMTP completed in {time.time()-start:.2f}s delivered={delivered} refused={refused}")
else:
print("No recipients to send to; skipping SMTP.")
# Only mark as processed if at least one recipient was delivered successfully
if delivered:
try:
mark_object_processed(bucket, key)
except Exception as e:
print("Failed to mark object processed after delivery:", e)
else:
print("No successful deliveries; NOT setting processed metadata so message can be re-evaluated later.")
return {
'statusCode': 200,
'body': f"processed={bool(delivered)}, delivered={delivered}, refused_count={len(refused)}"
}