diff --git a/install_postfix_advanced.sh b/install_postfix_advanced.sh
index b65d232..031f32a 100755
--- a/install_postfix_advanced.sh
+++ b/install_postfix_advanced.sh
@@ -1253,6 +1253,11 @@ id=BL_SENDER
 
 # Rate Limits
 
+# Throttle unknown clients to 5 recipients per 5 minutes:
+id=RATE_UNKNOWN_CLIENT_ADDR
+	client_name==unknown
+	action=rate(client_address/5/300/450 4.7.1 only 5 recipients per 5 minutes allowed)
+
 # Block clients (ip-addresses) sending more than 50 messages per minute exceeded. Error:RATE_CLIENT)
 id=RATE_CLIENT_ADDR
     &&INCOMING
diff --git a/install_postfwd.sh b/install_postfwd.sh
index 00113f5..f5861ef 100755
--- a/install_postfwd.sh
+++ b/install_postfwd.sh
@@ -440,6 +440,11 @@ id=BL_SENDER
 
 # Rate Limits
 
+# Throttle unknown clients to 5 recipients per 5 minutes:
+id=RATE_UNKNOWN_CLIENT_ADDR
+	client_name==unknown
+	action=rate(client_address/5/300/450 4.7.1 only 5 recipients per 5 minutes allowed)
+
 # Block clients (ip-addresses) sending more than 50 messages per minute exceeded. Error:RATE_CLIENT)
 id=RATE_CLIENT_ADDR
     &&INCOMING