Fixes #781. Add missing header for authenticated users if the option is enabled.

templates/main.cf.j2

@@ -645,6 +645,16 @@ smtpd_upstream_proxy_protocol = haproxy
 {% endif %}
 {% endif %}
 
+{% if postfix_add_missing_headers %}
+local_header_rewrite_clients =
+        permit_inet_interfaces
+{% if postfix_submission_server %}
+        permit_sasl_authenticated
+{% endif %}
+
+always_add_missing_headers = yes
+{% endif %}
+
 # FAST ETRN SERVICE
 #
 # Postfix maintains per-destination logfiles with information about