Discard ignored email

Create IgnoredEmail model

app/models.py

@@ -2293,3 +2293,10 @@ class Payout(db.Model, ModelMixin):
     comment = db.Column(db.Text)
 
     user = db.relationship(User)
+
+
+class IgnoredEmail(db.Model, ModelMixin):
+    """If an email has mail_from and rcpt_to present in this table, discard it by returning 250 status."""
+
+    mail_from = db.Column(db.String(512), nullable=False)
+    rcpt_to = db.Column(db.String(512), nullable=False)

email_handler.py

@@ -120,6 +120,7 @@ from app.models import (
     Mailbox,
     Bounce,
     TransactionalEmail,
+    IgnoredEmail,
 )
 from app.pgp_utils import PGPException, sign_data_with_pgpy, sign_data
 from app.utils import sanitize_email
@@ -1526,6 +1527,17 @@ def handle_bounce(envelope, email_log: EmailLog, msg: Message) -> str:
         return "550 SL E26 Email cannot be forwarded to mailbox"
 
 
+def should_ignore(mail_from: str, rcpt_tos: List[str]) -> bool:
+    if len(rcpt_tos) != 1:
+        return False
+
+    rcpt_to = rcpt_tos[0]
+    if IgnoredEmail.get_by(mail_from=mail_from, rcpt_to=rcpt_to):
+        return True
+
+    return False
+
+
 def handle(envelope: Envelope) -> str:
     """Return SMTP status"""
 
@@ -1535,6 +1547,10 @@ def handle(envelope: Envelope) -> str:
     envelope.mail_from = mail_from
     envelope.rcpt_tos = rcpt_tos
 
+    if should_ignore(mail_from, rcpt_tos):
+        LOG.e("Ignore email mail_from=%s rcpt_to=%s", mail_from, rcpt_tos)
+        return "250 email can't be sent from a reverse-alias"
+
     msg = email.message_from_bytes(envelope.original_content)
     postfix_queue_id = get_queue_id(msg)
     if postfix_queue_id:

migrations/versions/2021_062217_29ea13ed76f9_.py

@@ -0,0 +1,36 @@
+"""empty message
+
+Revision ID: 29ea13ed76f9
+Revises: a5e643d562c9
+Create Date: 2021-06-22 17:51:27.343947
+
+"""
+import sqlalchemy_utils
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '29ea13ed76f9'
+down_revision = 'a5e643d562c9'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.create_table('ignored_email',
+    sa.Column('id', sa.Integer(), autoincrement=True, nullable=False),
+    sa.Column('created_at', sqlalchemy_utils.types.arrow.ArrowType(), nullable=False),
+    sa.Column('updated_at', sqlalchemy_utils.types.arrow.ArrowType(), nullable=True),
+    sa.Column('mail_from', sa.String(length=512), nullable=False),
+    sa.Column('rcpt_to', sa.String(length=512), nullable=False),
+    sa.PrimaryKeyConstraint('id')
+    )
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_table('ignored_email')
+    # ### end Alembic commands ###

tests/test_email_handler.py

@@ -1,5 +1,5 @@
-from app.models import User, Alias, AuthorizedAddress
-from email_handler import get_mailbox_from_mail_from
+from app.models import User, Alias, AuthorizedAddress, IgnoredEmail
+from email_handler import get_mailbox_from_mail_from, should_ignore
 
 
 def test_get_mailbox_from_mail_from(flask_client):
@@ -32,3 +32,11 @@ def test_get_mailbox_from_mail_from(flask_client):
     )
     mb = get_mailbox_from_mail_from("unauthorized@gmail.com", alias)
     assert mb.email == "a@b.c"
+
+
+def test_should_ignore(flask_client):
+    assert should_ignore("mail_from", []) is False
+
+    assert not should_ignore("mail_from", ["rcpt_to"])
+    IgnoredEmail.create(mail_from="mail_from", rcpt_to="rcpt_to", commit=True)
+    assert should_ignore("mail_from", ["rcpt_to"])