diff --git a/postfix-filter.py b/postfix-filter.py
index fda9c86..542100d 100644
--- a/postfix-filter.py
+++ b/postfix-filter.py
@@ -163,6 +163,7 @@ class PostfixRspamdFilter:
         if not rspamd_result:
             # Se Rspamd non è disponibile, aggiungi header di fallback
             message['X-Spam-Status'] = 'Unknown (Rspamd not available)'
+            message['X-Spam-Flag'] = 'No'
             message['X-Spam-Checker-Version'] = 'Postfix Content Filter v1.0'
             return message
             
@@ -178,7 +179,11 @@ class PostfixRspamdFilter:
         is_spam = score >= required_score
         spam_status = f"{'Yes' if is_spam else 'No'}, score={score:.2f} required={required_score:.2f}"
         message['X-Spam-Status'] = spam_status
-        
+
+        # Header X-Spam-Flag: stesso esito di X-Spam-Status ma in forma sintetica,
+        # utile per regole client/server che filtrano su un singolo header booleano
+        message['X-Spam-Flag'] = 'Yes' if is_spam else 'No'
+
         # Header X-Spam-Score (punteggio numerico)
         message['X-Spam-Score'] = f"{score:.2f}"