diff --git a/core/postfix/conf/main.cf b/core/postfix/conf/main.cf
index fa442abf..d8c656c9 100644
--- a/core/postfix/conf/main.cf
+++ b/core/postfix/conf/main.cf
@@ -88,6 +88,7 @@ smtpd_recipient_restrictions =
   reject_non_fqdn_sender,
   reject_unknown_sender_domain,
   reject_unknown_recipient_domain,
+  reject_unverified_recipient,
   permit
 
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