diff --git a/server/messaging/reporting.py b/server/messaging/reporting.py
index 72eafb04d..a1c96fb68 100755
--- a/server/messaging/reporting.py
+++ b/server/messaging/reporting.py
@@ -99,6 +99,19 @@ def apply_timezone(data, fields):
 # ===============================================================================
 # REPORTING
 # ===============================================================================
+MAX_ALERT_DOWN_MINUTES = 100 * 365 * 24 * 60
+
+
+def get_alert_down_minutes():
+    """Return NTFPRCS_alert_down_time as whole minutes clamped to
+    0..MAX_ALERT_DOWN_MINUTES; a non-numeric value counts as 0."""
+    try:
+        minutes = int(get_setting_value("NTFPRCS_alert_down_time") or 0)
+    except (TypeError, ValueError):
+        return 0
+    return max(0, min(minutes, MAX_ALERT_DOWN_MINUTES))
+
+
 def get_notifications(db):
     """
     Fetch notifications for all configured sections.
@@ -129,7 +142,7 @@ def get_notifications(db):
 
     # Computed once and shared with NotificationInstance.clearPendingEmailFlag()
     # via conf, so the clear step acts on exactly the events selected here.
-    alert_down_minutes = int(get_setting_value("NTFPRCS_alert_down_time") or 0)
+    alert_down_minutes = get_alert_down_minutes()
     alert_down_cutoff = (
         timeNowUTC(as_string=False) - timedelta(minutes=alert_down_minutes)
     ).strftime(DATETIME_PATTERN)
diff --git a/server/models/notification_instance.py b/server/models/notification_instance.py
index 32a7fb2ef..d07229d2e 100755
--- a/server/models/notification_instance.py
+++ b/server/models/notification_instance.py
@@ -235,7 +235,8 @@ class NotificationInstance:
     def clearPendingEmailFlag(self):
         """Clear evePendingAlertEmail on reported Events and stamp
         devLastNotification on their devices; 'Device Down' events are only
-        cleared once NTFPRCS_alert_down_time minutes have passed."""
+        cleared if older than conf.down_alert_cutoff, the cutoff
+        get_notifications() used when selecting them."""
 
         # Clean Pending Alert Events
         self.db.sql.execute("""
diff --git a/test/backend/test_notification_down_clear_timezone.py b/test/backend/test_notification_down_clear_timezone.py
index bb2f8e929..1e629d6a4 100644
--- a/test/backend/test_notification_down_clear_timezone.py
+++ b/test/backend/test_notification_down_clear_timezone.py
@@ -275,5 +275,45 @@ class TestClearPendingEmailFlagSelectionCutoff(unittest.TestCase):
         self.assertLessEqual(cutoff_dt, after - timedelta(minutes=5))
 
 
+class TestAlertDownTimeBounds(unittest.TestCase):
+    """An out-of-range NTFPRCS_alert_down_time must never raise out of
+    get_notifications() (it runs inside the main monitoring loop)."""
+
+    def _run_get_notifications(self, raw_minutes):
+        """Run get_notifications() with the given raw setting value and return
+        the recorded cutoff as a UTC datetime, restoring conf afterward."""
+        mock_db = Mock()
+        mock_json_obj = Mock()
+        mock_json_obj.columnNames = []
+        mock_json_obj.json = {"data": []}
+        mock_db.get_table_as_json.return_value = mock_json_obj
+        settings = {
+            "NTFPRCS_INCLUDED_SECTIONS": ["down_devices"],
+            "NTFPRCS_alert_down_time": raw_minutes,
+        }
+        original_cutoff = conf.down_alert_cutoff
+        try:
+            with patch(
+                "messaging.reporting.get_setting_value",
+                side_effect=lambda key: settings.get(key, ""),
+            ):
+                get_notifications(mock_db)
+            cutoff = conf.down_alert_cutoff
+        finally:
+            conf.down_alert_cutoff = original_cutoff
+        return datetime.strptime(cutoff, DATETIME_PATTERN).replace(tzinfo=timezone.utc)
+
+    def test_huge_value_does_not_raise(self):
+        """A value too large for timedelta/datetime must be bounded, not raise
+        OverflowError."""
+        cutoff = self._run_get_notifications("999999999999999")
+        self.assertLess(cutoff, timeNowUTC(as_string=False))
+
+    def test_negative_value_does_not_produce_future_cutoff(self):
+        """A negative window must not push the cutoff into the future."""
+        cutoff = self._run_get_notifications("-5")
+        self.assertLessEqual(cutoff, timeNowUTC(as_string=False))
+
+
 if __name__ == "__main__":
     unittest.main()