diff --git a/HowtoPostfix.md b/HowtoPostfix.md
index 38fe13fd..19adecde 100644
--- a/HowtoPostfix.md
+++ b/HowtoPostfix.md
@@ -60,6 +60,7 @@ recipient_delimiter = +
 inet_interfaces = all
 inet_protocols = ipv4
 disable_vrfy_command = yes
+smtpd_relay_restrictions = permit_mynetworks defer_unauth_destination
 ~~~
 
 ### Configuration minimale pour serveur web