return 550 instead of 421 in case of SMTPRecipientsRefused

app/email/status.py

@@ -9,7 +9,7 @@ E205 = "250 SL E205 bounce handled"
 E206 = "250 SL E206 Out of office"
 
 # 4** errors
-E401 = "421 SL E401 Retry later"
+# E401 = "421 SL E401 Retry later"
 E402 = "421 SL E402 Retry later"
 E403 = "421 SL E403 Retry later"
 E404 = "421 SL E404 Retry later"
@@ -36,4 +36,5 @@ E516 = "550 SL E516 invalid mailbox"
 E517 = "550 SL E517 unverified mailbox"
 E518 = "550 SL E518 Disabled mailbox"
 E519 = "550 SL E519 Email detected as spam"
-E520 = "550 SL E24 Email cannot be sent to contact"
+E520 = "550 SL E520 Email cannot be sent to contact"
+E521 = "550 SL E521 Cannot reach mailbox"

email_handler.py

@@ -751,7 +751,7 @@ def forward_email_to_mailbox(
             alias,
             mailbox,
         )
-        return False, status.E401
+        return False, status.E521
     else:
         db.session.commit()
         return True, status.E200