diff --git a/data/conf/postfix/master.cf b/data/conf/postfix/master.cf
index 79642f6d..efc311a5 100644
--- a/data/conf/postfix/master.cf
+++ b/data/conf/postfix/master.cf
@@ -2,6 +2,7 @@ smtp       inet  n       -       n       -       1       postscreen
 smtpd      pass  -       -       n       -       -       smtpd
   -o smtpd_helo_restrictions=permit_mynetworks,reject_non_fqdn_helo_hostname
   -o smtpd_sasl_auth_enable=no
+  -o smtpd_sender_restrictions=permit_mynetworks,reject_unlisted_sender,reject_unknown_sender_domain
 smtps    inet  n       -       n       -       -       smtpd
   -o smtpd_tls_wrappermode=yes
   -o smtpd_client_restrictions=permit_mynetworks,permit_sasl_authenticated,reject