diff --git a/src/apps/storetool/bongo/storetool/BackupCommands.py b/src/apps/storetool/bongo/storetool/BackupCommands.py
index 942e283..effa84c 100644
--- a/src/apps/storetool/bongo/storetool/BackupCommands.py
+++ b/src/apps/storetool/bongo/storetool/BackupCommands.py
@@ -35,9 +35,13 @@ from bongo.storetool.Connection import connect_store
 _METADATA_PREFIX = "BONGO."
 _GENERATED_PROPERTIES = {
     "nmap.collection",
+    "nmap.created",
     "nmap.flags",
     "nmap.guid",
     "nmap.index",
+    "nmap.lastmodified",
+    "nmap.length",
+    "nmap.mail.imapuid",
     "nmap.type",
 }
 
diff --git a/src/apps/storetool/tests/test_backup_commands.py b/src/apps/storetool/tests/test_backup_commands.py
index f88ebd7..25cb7d4 100644
--- a/src/apps/storetool/tests/test_backup_commands.py
+++ b/src/apps/storetool/tests/test_backup_commands.py
@@ -53,7 +53,14 @@ class BackupArchiveTests(unittest.TestCase):
 
     def test_metadata_round_trip_keeps_user_properties(self):
         metadata = _metadata(
-            _Item(), {"nmap.guid": "generated", "display": "Grüße"})
+            _Item(), {
+                "nmap.guid": "generated",
+                "nmap.created": "2026-07-23 12:00:00Z",
+                "nmap.lastmodified": "2026-07-23 12:01:00Z",
+                "nmap.length": "42",
+                "nmap.mail.imapuid": "00000007",
+                "display": "Grüße",
+            })
         self.assertEqual(metadata["BONGO.imapuid"], "7")
         self.assertEqual(_properties(metadata), {"display": "Grüße"})