diff --git a/install_postfix_advanced.sh b/install_postfix_advanced.sh
index 114d3dd..b6d56fa 100755
--- a/install_postfix_advanced.sh
+++ b/install_postfix_advanced.sh
@@ -1255,6 +1255,7 @@ id=BL_SENDER
 
 # Throttle unknown clients to 5 recipients per 5 minutes:
 id=RATE_UNKNOWN_CLIENT_ADDR
+   sasl_username =~ /^$/
 	client_name==unknown
 	action=rate(client_address/5/300/450 4.7.1 only 5 recipients per 5 minutes allowed)
 
diff --git a/install_postfwd.sh b/install_postfwd.sh
index f5861ef..bdbd3e2 100755
--- a/install_postfwd.sh
+++ b/install_postfwd.sh
@@ -442,6 +442,7 @@ id=BL_SENDER
 
 # Throttle unknown clients to 5 recipients per 5 minutes:
 id=RATE_UNKNOWN_CLIENT_ADDR
+   sasl_username =~ /^$/
 	client_name==unknown
 	action=rate(client_address/5/300/450 4.7.1 only 5 recipients per 5 minutes allowed)