Merge ~hloeung/mailman3-core-charm:master into mailman3-core-charm:master

[Haw Loeung]

Reject for recipients we don't know about - LP:1817822

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

This merge proposal is being monitored by mergebot. Change the status to Approved to merge.

[Alexandre Gomes (alejdg)]

review: Approve

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

Change successfully merged at revision 9aa6c90122ca8f988e742120e68f4ef50d78406d

diff --git a/reactive/mailman3_core.py b/reactive/mailman3_core.py
index c26337f..4334c05 100644
--- a/reactive/mailman3_core.py
+++ b/reactive/mailman3_core.py
@@ -91,12 +91,15 @@ def configure_postfix():
                              'smtpd_relay_restrictions=permit_mynetworks defer_unauth_destination'])
     if os.path.exists('/var/lib/mailman3/data/postfix_lmtp'):
         subprocess.check_output(['postconf', 'transport_maps=hash:/var/lib/mailman3/data/postfix_lmtp',
+                                 'relay_recipient_maps=hash:/var/lib/mailman3/data/postfix_lmtp',
                                  'local_recipient_maps=hash:/var/lib/mailman3/data/postfix_lmtp'])
         subprocess.check_output(['postmap', '/var/lib/mailman3/data/postfix_lmtp'])
     if os.path.exists('/var/lib/mailman3/data/postfix_domains'):
         subprocess.check_output(['postconf', 'relay_domains=hash:/var/lib/mailman3/data/postfix_domains'])
         subprocess.check_output(['postmap', '/var/lib/mailman3/data/postfix_domains'])
 
+    subprocess.check_output(['postmap', 'smtpd_sender_restrictions=reject_unknown_sender_domain'])
+
     # HyperKitty expects messages will all have the 'Message-ID' header,
     # unfortunately not all clients do so let's work around it (LP: #1776658)
     subprocess.check_output(['postconf', 'always_add_missing_headers=yes',