Merge pull request #226 from simple-login/sender-report

Handle transactional bounce emails

app/config.py

@@ -62,6 +62,12 @@ except Exception:
 # maximum number of directory a premium user can create
 MAX_NB_DIRECTORY = 50
 
+# transactional email sender
+SENDER = os.environ.get("SENDER")
+
+# the directory to store bounce emails
+SENDER_DIR = os.environ.get("SENDER_DIR")
+
 ENFORCE_SPF = "ENFORCE_SPF" in os.environ
 
 # allow to override postfix server locally

app/email_utils.py

@@ -27,6 +27,7 @@ from app.config import (
     DISPOSABLE_EMAIL_DOMAINS,
     MAX_ALERT_24H,
     POSTFIX_PORT,
+    SENDER,
 )
 from app.dns_utils import get_mx_domains
 from app.extensions import db
@@ -180,9 +181,7 @@ def send_cannot_create_domain_alias(user, alias, domain):
     )
 
 
-def send_email(
-    to_email, subject, plaintext, html=None, bounced_email: Optional[Message] = None
-):
+def send_email(to_email, subject, plaintext, html=None):
     if NOT_SEND_EMAIL:
         LOG.d(
             "send email with subject %s to %s, plaintext: %s",
@@ -200,26 +199,12 @@ def send_email(
     else:
         smtp = SMTP(POSTFIX_SERVER, POSTFIX_PORT or 25)
 
-    if bounced_email:
-        msg = MIMEMultipart("mixed")
+    msg = MIMEMultipart("alternative")
+    msg.attach(MIMEText(plaintext, "text"))
 
-        # add email main body
-        body = MIMEMultipart("alternative")
-        body.attach(MIMEText(plaintext, "text"))
-        if html:
-            body.attach(MIMEText(html, "html"))
-
-        msg.attach(body)
-
-        # add attachment
-        rfcmessage = MIMEBase("message", "rfc822")
-        rfcmessage.attach(bounced_email)
-        msg.attach(rfcmessage)
-    else:
-        msg = MIMEMultipart("alternative")
-        msg.attach(MIMEText(plaintext, "text"))
-        if html:
-            msg.attach(MIMEText(html, "html"))
+    if not html:
+        html = plaintext.replace("\n", "<br>")
+    msg.attach(MIMEText(html, "html"))
 
     msg["Subject"] = subject
     msg["From"] = f"{SUPPORT_NAME} <{SUPPORT_EMAIL}>"
@@ -236,7 +221,10 @@ def send_email(
     add_dkim_signature(msg, email_domain)
 
     msg_raw = msg.as_bytes()
-    smtp.sendmail(SUPPORT_EMAIL, to_email, msg_raw)
+    if SENDER:
+        smtp.sendmail(SENDER, to_email, msg_raw)
+    else:
+        smtp.sendmail(SUPPORT_EMAIL, to_email, msg_raw)
 
 
 def send_email_with_rate_control(
@@ -246,7 +234,6 @@ def send_email_with_rate_control(
     subject,
     plaintext,
     html=None,
-    bounced_email: Optional[Message] = None,
     max_alert_24h=MAX_ALERT_24H,
 ) -> bool:
     """Same as send_email with rate control over alert_type.
@@ -273,7 +260,7 @@ def send_email_with_rate_control(
 
     SentAlert.create(user_id=user.id, alert_type=alert_type, to_email=to_email)
     db.session.commit()
-    send_email(to_email, subject, plaintext, html, bounced_email)
+    send_email(to_email, subject, plaintext, html)
     return True
 
 

email_handler.py

@@ -31,6 +31,7 @@ It should contain the following info:
 
 """
 import email
+import os
 import time
 import uuid
 from email import encoders
@@ -63,6 +64,8 @@ from app.config import (
     ALERT_SPAM_EMAIL,
     ALERT_SPF,
     POSTFIX_PORT,
+    SENDER,
+    SENDER_DIR,
 )
 from app.email_utils import (
     send_email,
@@ -836,7 +839,6 @@ def handle_bounce(contact: Contact, alias: Alias, msg: Message, user: User):
         send_email_with_rate_control(
             user,
             ALERT_BOUNCE_EMAIL,
-            # use user mail here as only user is authenticated to see the refused email
             user.email,
             f"Email from {contact.website_email} to {address} cannot be delivered to your inbox",
             render(
@@ -857,8 +859,6 @@ def handle_bounce(contact: Contact, alias: Alias, msg: Message, user: User):
                 refused_email_url=refused_email_url,
                 mailbox_email=mailbox.email,
             ),
-            # cannot include bounce email as it can contain spammy text
-            # bounced_email=msg,
         )
     # disable the alias the second time email is bounced
     elif nb_bounced >= 2:
@@ -876,7 +876,6 @@ def handle_bounce(contact: Contact, alias: Alias, msg: Message, user: User):
         send_email_with_rate_control(
             user,
             ALERT_BOUNCE_EMAIL,
-            # use user mail here as only user is authenticated to see the refused email
             user.email,
             f"Alias {address} has been disabled due to second undelivered email from {contact.website_email}",
             render(
@@ -895,8 +894,6 @@ def handle_bounce(contact: Contact, alias: Alias, msg: Message, user: User):
                 refused_email_url=refused_email_url,
                 mailbox_email=mailbox.email,
             ),
-            # cannot include bounce email as it can contain spammy text
-            # bounced_email=msg,
         )
 
 
@@ -1025,6 +1022,27 @@ def handle_unsubscribe(envelope: Envelope):
     return "250 Unsubscribe request accepted"
 
 
+def handle_sender_email(envelope: Envelope):
+    filename = (
+        arrow.now().format("YYYY-MM-DD_HH-mm-ss") + "_" + random_string(10) + ".eml"
+    )
+    filepath = os.path.join(SENDER_DIR, filename)
+
+    with open(filepath, "wb") as f:
+        f.write(envelope.original_content)
+
+    LOG.d("Write email to sender at %s", filepath)
+
+    msg = email.message_from_bytes(envelope.original_content)
+    orig = get_orig_message_from_bounce(msg)
+    if orig:
+        LOG.warning(
+            "Original message %s -> %s saved at %s", orig["From"], orig["To"], filepath
+        )
+
+    return "250 email to sender accepted"
+
+
 def handle(envelope: Envelope, smtp: SMTP) -> str:
     """Return SMTP status"""
     # unsubscribe request
@@ -1032,6 +1050,11 @@ def handle(envelope: Envelope, smtp: SMTP) -> str:
         LOG.d("Handle unsubscribe request from %s", envelope.mail_from)
         return handle_unsubscribe(envelope)
 
+    # emails sent to sender. Probably bounce emails
+    if SENDER and envelope.rcpt_tos == [SENDER]:
+        LOG.d("Handle email sent to sender from %s", envelope.mail_from)
+        return handle_sender_email(envelope)
+
     # Whether it's necessary to apply greylisting
     if greylisting_needed(envelope.mail_from, envelope.rcpt_tos):
         LOG.warning(

example.env

@@ -33,6 +33,11 @@ ALIAS_DOMAINS=["domain1.com", "domain2.com"]
 # transactional email is sent from this email address
 SUPPORT_EMAIL=support@sl.local
 SUPPORT_NAME=Son from SimpleLogin
+# in case sender is different than SUPPORT_EMAIL
+SENDER=sender@sl.local
+
+# all emails sent to sender are stored in this folder
+SENDER_DIR=/tmp
 
 # to receive general stats.
 # ADMIN_EMAIL=admin@sl.local