fix(mailgun): improve DMARC report detection to prevent parsing errors

- Add multiple DMARC detection methods (subject, sender, raw_content)
- Handle DMARC reports without body content
- Prevent 'name or message missing' errors for DMARC emails
- Add better logging for DMARC report detection

Author: sanyo4ever

keep/providers/mailgun_provider/mailgun_provider.py

@@ -287,11 +287,33 @@ def _format_alert(
         message = event.get("stripped-text", body_plain)
         raw_content = event.get("raw_content")
 
+        # Check for DMARC reports in multiple ways
+        is_dmarc_report = False
+        
+        # Check raw_content if available
         if isinstance(raw_content, bytes) and b"dmarc" in raw_content.lower():
-            logger.warning("DMARC alert detected, skipping")
-            return None
+            is_dmarc_report = True
         elif isinstance(raw_content, str) and "dmarc" in raw_content.lower():
-            logger.warning("DMARC alert detected, skipping")
+            is_dmarc_report = True
+        
+        # Check subject for DMARC report patterns
+        if name and ("dmarc" in name.lower() or "report domain:" in name.lower()):
+            is_dmarc_report = True
+            
+        # Check sender for DMARC report senders
+        if source and any(dmarc_sender in source.lower() for dmarc_sender in [
+            "noreply-dmarc-support@google.com",
+            "dmarc-support@google.com",
+            "dmarc@",
+            "postmaster@"
+        ]):
+            is_dmarc_report = True
+            
+        if is_dmarc_report:
+            logger.warning("DMARC alert detected, skipping", extra={
+                "from": source,
+                "subject": name
+            })
             return None
 
         if not name or not message: