diff --git a/parsedmarc/mail/graph.py b/parsedmarc/mail/graph.py
index b8c02bb5..9595a85d 100644
--- a/parsedmarc/mail/graph.py
+++ b/parsedmarc/mail/graph.py
@@ -93,6 +93,15 @@ def _generate_credential(auth_method: str, token_path: Path, **kwargs):
 
 
 class MSGraphConnection(MailboxConnection):
+    _WELL_KNOWN_FOLDERS = {
+        "inbox": "inbox",
+        "archive": "archive",
+        "drafts": "drafts",
+        "sentitems": "sentitems",
+        "deleteditems": "deleteditems",
+        "junkemail": "junkemail",
+    }
+
     def __init__(
         self,
         auth_method: str,
@@ -267,8 +276,25 @@ class MSGraphConnection(MailboxConnection):
                 parent_folder_id = folder_id
             return self._find_folder_id_with_parent(path_parts[-1], parent_folder_id)
         else:
+            # Shared mailboxes can fail root listing; try well-known folders first.
+            well_known_folder_id = self._get_well_known_folder_id(folder_name)
+            if well_known_folder_id:
+                return well_known_folder_id
             return self._find_folder_id_with_parent(folder_name, None)
 
+    def _get_well_known_folder_id(self, folder_name: str) -> Optional[str]:
+        folder_key = folder_name.lower().replace(" ", "").replace("-", "")
+        alias = self._WELL_KNOWN_FOLDERS.get(folder_key)
+        if alias is None:
+            return None
+
+        url = f"/users/{self.mailbox_name}/mailFolders/{alias}?$select=id,displayName"
+        folder_resp = self._client.get(url)
+        if folder_resp.status_code != 200:
+            return None
+        payload = folder_resp.json()
+        return payload.get("id")
+
     def _find_folder_id_with_parent(
         self, folder_name: str, parent_folder_id: Optional[str]
     ):
@@ -279,6 +305,10 @@ class MSGraphConnection(MailboxConnection):
         filter = f"?$filter=displayName eq '{folder_name}'"
         folders_resp = self._request_with_retries("get", url + filter)
         if folders_resp.status_code != 200:
+            if parent_folder_id is None:
+                well_known_folder_id = self._get_well_known_folder_id(folder_name)
+                if well_known_folder_id:
+                    return well_known_folder_id
             raise RuntimeWarning(f"Failed to list folders.{folders_resp.json()}")
         folders: list = folders_resp.json()["value"]
         matched_folders = [
diff --git a/tests.py b/tests.py
index 4ab6fb15..5941070c 100755
--- a/tests.py
+++ b/tests.py
@@ -468,6 +468,8 @@ hosts = localhost
         self.assertEqual(ctx.exception.code, 1)
         mock_save_aggregate.assert_called_once()
         mock_save_forensic_opensearch.assert_called_once()
+
+
 class _FakeGraphResponse:
     def __init__(self, status_code, payload=None, text=""):
         self.status_code = status_code
@@ -477,6 +479,7 @@ class _FakeGraphResponse:
     def json(self):
         return self._payload
 
+
 class _BreakLoop(BaseException):
     pass
 
@@ -1210,5 +1213,52 @@ since = 2d
 
         self.assertEqual(system_exit.exception.code, 1)
         self.assertEqual(mock_watch_inbox.call_args.kwargs.get("since"), "2d")
+
+class _FakeGraphClient:
+    def get(self, url, params=None):
+        if "/mailFolders/inbox?$select=id,displayName" in url:
+            return _FakeGraphResponse(200, {"id": "inbox-id", "displayName": "Inbox"})
+
+        if "/mailFolders?$filter=displayName eq 'Inbox'" in url:
+            return _FakeGraphResponse(
+                404,
+                {
+                    "error": {
+                        "code": "ErrorItemNotFound",
+                        "message": "Default folder Root not found.",
+                    }
+                },
+            )
+
+        if "/mailFolders?$filter=displayName eq 'Custom'" in url:
+            return _FakeGraphResponse(
+                404,
+                {
+                    "error": {
+                        "code": "ErrorItemNotFound",
+                        "message": "Default folder Root not found.",
+                    }
+                },
+            )
+
+        return _FakeGraphResponse(404, {"error": {"code": "NotFound"}})
+
+
+class TestMSGraphFolderFallback(unittest.TestCase):
+    def testWellKnownFolderFallback(self):
+        connection = MSGraphConnection.__new__(MSGraphConnection)
+        connection.mailbox_name = "shared@example.com"
+        connection._client = _FakeGraphClient()
+
+        folder_id = connection._find_folder_id_from_folder_path("Inbox")
+        self.assertEqual(folder_id, "inbox-id")
+
+    def testUnknownFolderStillFails(self):
+        connection = MSGraphConnection.__new__(MSGraphConnection)
+        connection.mailbox_name = "shared@example.com"
+        connection._client = _FakeGraphClient()
+
+        with self.assertRaises(RuntimeWarning):
+            connection._find_folder_id_from_folder_path("Custom")
 if __name__ == "__main__":
     unittest.main(verbosity=2)