Ensure gmail works for personal accounts (#3541)

* Ensure gmail works for personal accounts

* nit

* minor update

backend/onyx/connectors/gmail/connector.py

@@ -4,6 +4,7 @@ from typing import Dict
 
 from google.oauth2.credentials import Credentials as OAuthCredentials  # type: ignore
 from google.oauth2.service_account import Credentials as ServiceAccountCredentials  # type: ignore
+from googleapiclient.errors import HttpError  # type: ignore
 
 from onyx.configs.app_configs import INDEX_BATCH_SIZE
 from onyx.configs.constants import DocumentSource
@@ -249,6 +250,13 @@ class GmailConnector(LoadConnector, PollConnector, SlimConnector):
         return new_creds_dict
 
     def _get_all_user_emails(self) -> list[str]:
+        """
+        List all user emails if we are on a Google Workspace domain.
+        If the domain is gmail.com, or if we attempt to call the Admin SDK and
+        get a 404, fall back to using the single user.
+        """
+
+        try:
             admin_service = get_admin_service(self.creds, self.primary_admin_email)
             emails = []
             for user in execute_paginated_retrieval(
@@ -261,6 +269,18 @@ class GmailConnector(LoadConnector, PollConnector, SlimConnector):
                     emails.append(email)
             return emails
 
+        except HttpError as e:
+            if e.resp.status == 404:
+                logger.warning(
+                    "Received 404 from Admin SDK; this may indicate a personal Gmail account "
+                    "with no Workspace domain. Falling back to single user."
+                )
+                return [self.primary_admin_email]
+            raise
+
+        except Exception:
+            raise
+
     def _fetch_threads(
         self,
         time_range_start: SecondsSinceUnixEpoch | None = None,