diff --git a/email_api/email_api/app.py b/email_api/email_api/app.py
index 2006c1f..7d2809c 100644
--- a/email_api/email_api/app.py
+++ b/email_api/email_api/app.py
@@ -175,6 +175,7 @@ def retry_domain_emails(domain):
         return jsonify({'error': 'Unauthorized'}), 401
 
     bucket = domain.replace('.', '-') + '-emails'
+    # 1) Sammle alle Keys, die noch nicht processed=true sind
     unprocessed = []
     paginator = s3_client.get_paginator('list_objects_v2')
     for page in paginator.paginate(Bucket=bucket):
@@ -182,33 +183,64 @@ def retry_domain_emails(domain):
             head = s3_client.head_object(Bucket=bucket, Key=obj['Key'])
             if head.get('Metadata', {}).get('processed') != 'true':
                 unprocessed.append(obj['Key'])
-    
+
     request_id = f"retry-{domain}-{int(time.time())}"
-    logger.info(f"[{request_id}] RETRY processing for domain={domain}, keys={unprocessed}")
-    
+    logger.info(f"[{request_id}] RETRY for domain={domain}, keys={unprocessed}")
+
     results = {'processed': [], 'failed': []}
+
     for key in unprocessed:
         try:
+            # E-Mail laden und parsen
             body = s3_client.get_object(Bucket=bucket, Key=key)['Body'].read()
             msg = BytesParser(policy=default).parsebytes(body)
-            from_addr = getaddresses(msg.get_all('from', []))[0][1] if msg.get_all('from') else f'retry@{domain}'
-            to_addrs = [addr for _n, addr in getaddresses(msg.get_all('to', []))]
-            cc_addrs = [addr for _n, addr in getaddresses(msg.get_all('cc', []))]
+            from_addr = (
+                getaddresses(msg.get_all('from', []))[0][1]
+                if msg.get_all('from') else f'retry@{domain}'
+            )
+            to_addrs  = [addr for _n, addr in getaddresses(msg.get_all('to', []))]
+            cc_addrs  = [addr for _n, addr in getaddresses(msg.get_all('cc', []))]
             bcc_addrs = [addr for _n, addr in getaddresses(msg.get_all('bcc', []))]
             recipients = to_addrs + cc_addrs + bcc_addrs
 
-            with smtplib.SMTP(SMTP_HOST, SMTP_PORT) as smtp:
-                smtp.sendmail(from_addr, recipients, body)
+            if not recipients:
+                # keine Empfänger → nichts markieren
+                results['failed'].append(f"{key}: no recipients")
+                continue
 
-            if mark_email_as_processed(bucket, key):
+            try:
+                # Versuch, die Mail zuzustellen
+                with smtplib.SMTP(SMTP_HOST, SMTP_PORT) as smtp:
+                    smtp.sendmail(from_addr, recipients, body)
+
+                # bei Erfolg → processed=true
+                mark_email_as_processed(bucket, key, 'true')
                 results['processed'].append(key)
-            else:
-                results['failed'].append(key)
+
+            except smtplib.SMTPRecipientsRefused as e:
+                # bei abgelehnten Adressen → unknownUser vs unknownDomain
+                refused = e.recipients  # dict: {addr: (code, msg), ...}
+                # check, ob eine abgelehnte Adresse zur eigenen Domain gehört
+                if any(addr.split('@')[-1] == domain for addr in refused):
+                    status = 'unknownUser'
+                else:
+                    status = 'unknownDomain'
+
+                mark_email_as_processed(bucket, key, status)
+                results['processed'].append(key)
+                results['failed'].append({key: refused})
+
+            except Exception as e:
+                # andere SMTP-/Verbindungs-Fehler → nicht markieren
+                results['failed'].append(f"{key}: {e}")
+
         except Exception as e:
+            # Fehler beim Laden/Parsen der Objekte
             results['failed'].append(f"{key}: {e}")
 
     return jsonify(results), 200
 
+
 @app.route('/health', methods=['GET'])
 def health_check():
     return jsonify({'status': 'OK'}), 200