diff --git a/site-cookbooks/kosmos-postfix/recipes/default.rb b/site-cookbooks/kosmos-postfix/recipes/default.rb
index 1afd892..c689928 100644
--- a/site-cookbooks/kosmos-postfix/recipes/default.rb
+++ b/site-cookbooks/kosmos-postfix/recipes/default.rb
@@ -21,5 +21,6 @@ node.default["postfix"]["sasl"] = {
 node.default["postfix"]["main"]["relayhost"]                  = smtp_credentials["relayhost"]
 node.default["postfix"]["main"]["smtp_sasl_auth_enable"]      = "yes"
 node.default["postfix"]["main"]["smtp_sasl_security_options"] = "noanonymous"
+node.default["postfix"]["main"]["smtpd_relay_restrictions"] = "permit_mynetworks, reject"
 
 include_recipe "postfix::default"