diff --git a/backend/app/services/external_reply_service.py b/backend/app/services/external_reply_service.py
index 1a82ea9..bd7a3ad 100644
--- a/backend/app/services/external_reply_service.py
+++ b/backend/app/services/external_reply_service.py
@@ -48,15 +48,29 @@ class ExternalReplyPlan:
 
 
 def internet_message_id_of(message: dict) -> str | None:
-    stored = canonical_message_id(
-        message.get("internet_message_id") or message.get("message_id")
-    )
-    raw_header = (message.get("raw_headers") or {}).get("message_id")
-    raw_canonical = canonical_message_id(raw_header)
-    if raw_canonical and stored:
-        if folded_message_id(raw_canonical) == folded_message_id(stored):
-            return raw_canonical
-    return stored or raw_canonical
+    return internet_message_id_of_message(message)
+
+
+async def resolve_internet_message_id(database, message: dict) -> str | None:
+    """Resolve parent Message-ID, recovering Gmail case from stored raw MIME when needed."""
+    resolved = internet_message_id_of_message(message)
+    if resolved:
+        return resolved
+
+    raw_mime = message.get("raw_mime")
+    if not raw_mime:
+        return None
+
+    try:
+        raw = await get_raw_mime_storage().get(raw_mime)
+        parsed = parse_mime(raw)
+        return first_message_id(parsed.get("message_id"))
+    except Exception:
+        logger.exception(
+            "failed_to_resolve_message_id_from_raw_mime message_id=%s",
+            message.get("_id"),
+        )
+        return None
 
 
 async def resolve_external_reply_parent(