diff --git a/ses-lambda/lambda-function.py b/ses-lambda/lambda-function.py
index 29e8255..8a1a7ea 100644
--- a/ses-lambda/lambda-function.py
+++ b/ses-lambda/lambda-function.py
@@ -19,20 +19,22 @@ MAX_EMAIL_SIZE = int(os.environ.get('MAX_EMAIL_SIZE', '10485760'))
 s3_client = boto3.client('s3')
 
 def mark_email_processed(bucket, key, s3_client, processor='lambda'):
-    """Setzt in S3 das processed-Flag per Metadata."""
-    s3_client.copy_object(
-        Bucket=bucket,
-        Key=key,
-        CopySource={'Bucket': bucket, 'Key': key},
-        Metadata={
-            'processed': 'true',
-            'processed_timestamp': str(int(time.time())),
-            'processor': processor
-        },
-        MetadataDirective='REPLACE'
-    )
-    logger.info(f"Marked S3 object {bucket}/{key} as processed")
-
+    try:
+        s3_client.copy_object(
+            Bucket=bucket,
+            Key=key,
+            CopySource={'Bucket': bucket, 'Key': key},
+            Metadata={
+                'processed': 'true',
+                'processed_timestamp': str(int(time.time())),
+                'processor': processor
+            },
+            MetadataDirective='REPLACE'
+        )
+        logger.info(f"Marked S3 object {bucket}/{key} as processed")
+    except botocore.exceptions.ClientError as e:
+        logger.error(f"Fehler beim Markieren {bucket}/{key}: {e}")
+    
 def call_api_once(payload, domain, request_id):
     """Single-shot POST, kein Retry."""
     url = f"{API_BASE_URL}/process/{domain}"
@@ -64,6 +66,12 @@ def lambda_handler(event, context):
 
     # Kopf-Check
     head = s3_client.head_object(Bucket=bucket, Key=key)
+    
+    metadata = head.get('Metadata', {})
+    if metadata.get('processed') == 'true':
+        logger.info(f"[{req_id}] Skipping already processed object")
+        return {'statusCode': 200, 'body': 'Already processed'}
+
     size = head['ContentLength']
     if size > MAX_EMAIL_SIZE:
         logger.warning(f"[{req_id}] Email too large: {size} bytes")