do not send bounce to IgnoreBounceSender

app/email/status.py

@@ -8,6 +8,9 @@ E205 = "250 SL E205 bounce handled"
 # out of office status
 E206 = "250 SL E206 Out of office"
 
+# if mail_from is a IgnoreBounceSender, no need to send back a bounce report
+E207 = "250 SL E207 No bounce report"
+
 # 4** errors
 # E401 = "421 SL E401 Retry later"
 E402 = "421 SL E402 Encryption failed - Retry later"

app/email_utils.py

@@ -58,6 +58,7 @@ from app.models import (
     Alias,
     EmailLog,
     TransactionalEmail,
+    IgnoreBounceSender,
 )
 from app.utils import (
     random_string,
@@ -1213,3 +1214,11 @@ def get_queue_id(msg: Message) -> Optional[str]:
     with_esmtps = received_header[search_result.start() : search_result.end()]
 
     return with_esmtps[len("with ESMTPS id ") :]
+
+
+def should_ignore_bounce(mail_from: str) -> bool:
+    if IgnoreBounceSender.get_by(mail_from=mail_from):
+        LOG.w("do not send back bounce report to %s", mail_from)
+        return True
+
+    return False

email_handler.py

@@ -111,6 +111,7 @@ from app.email_utils import (
     sl_sendmail,
     sanitize_header,
     get_queue_id,
+    should_ignore_bounce,
 )
 from app.extensions import db
 from app.log import LOG, set_message_id
@@ -540,13 +541,19 @@ def handle_forward(envelope, msg: Message, rcpt_to: str) -> List[Tuple[bool, str
         alias = try_auto_create(address)
         if not alias:
             LOG.d("alias %s cannot be created on-the-fly, return 550", address)
-            return [(False, status.E515)]
+            if should_ignore_bounce(envelope.mail_from):
+                return [(True, status.E207)]
+            else:
+                return [(False, status.E515)]
 
     user = alias.user
 
     if user.disabled:
         LOG.w("User %s disabled, disable forwarding emails for %s", user, alias)
-        return [(False, status.E504)]
+        if should_ignore_bounce(envelope.mail_from):
+            return [(True, status.E207)]
+        else:
+            return [(False, status.E504)]
 
     # mail_from = envelope.mail_from
     # for mb in alias.mailboxes:
@@ -588,7 +595,10 @@ def handle_forward(envelope, msg: Message, rcpt_to: str) -> List[Tuple[bool, str
 
     # no valid mailbox
     if not mailboxes:
-        return [(False, status.E516)]
+        if should_ignore_bounce(envelope.mail_from):
+            return [(True, status.E207)]
+        else:
+            return [(False, status.E516)]
 
     # no need to create a copy of message
     for mailbox in mailboxes:
@@ -618,8 +628,11 @@ def forward_email_to_mailbox(
     LOG.d("Forward %s -> %s -> %s", contact, alias, mailbox)
 
     if mailbox.disabled:
-        LOG.debug("%s disabled, do not forward")
-        return False, status.E518
+        LOG.d("%s disabled, do not forward")
+        if should_ignore_bounce(envelope.mail_from):
+            return True, status.E207
+        else:
+            return False, status.E518
 
     # sanity check: make sure mailbox is not actually an alias
     if get_email_domain_part(alias.email) == get_email_domain_part(mailbox.email):
@@ -819,7 +832,10 @@ def forward_email_to_mailbox(
             alias,
             mailbox,
         )
-        return False, status.E521
+        if should_ignore_bounce(envelope.mail_from):
+            return True, status.E207
+        else:
+            return False, status.E521
     else:
         db.session.commit()
         return True, status.E200
@@ -1707,7 +1723,10 @@ def handle(envelope: Envelope) -> str:
 
     if rate_limited(mail_from, rcpt_tos):
         LOG.w("Rate Limiting applied for mail_from:%s rcpt_tos:%s", mail_from, rcpt_tos)
-        return status.E522
+        if should_ignore_bounce(envelope.mail_from):
+            return status.E207
+        else:
+            return status.E522
 
     # Handle "out of office" auto notice. An automatic response is sent for every forwarded email
     # todo: remove logging

tests/test_email_utils.py

@@ -28,9 +28,10 @@ from app.email_utils import (
     decode_text,
     parse_id_from_bounce,
     get_queue_id,
+    should_ignore_bounce,
 )
 from app.extensions import db
-from app.models import User, CustomDomain, Alias, Contact, EmailLog
+from app.models import User, CustomDomain, Alias, Contact, EmailLog, IgnoreBounceSender
 
 # flake8: noqa: E101, W191
 from tests.utils import login
@@ -740,3 +741,10 @@ def test_get_queue_id():
     )
 
     assert get_queue_id(msg) == "4FxQmw1DXdz2vK2"
+
+
+def test_should_ignore_bounce(flask_client):
+    assert not should_ignore_bounce("not-exist")
+
+    IgnoreBounceSender.create(mail_from="to-ignore@example.com")
+    assert should_ignore_bounce("to-ignore@example.com")