diff --git a/cookbook/logging/monolog_email.rst b/cookbook/logging/monolog_email.rst
index c3ef1e147b1..d8127cb8fe5 100644
--- a/cookbook/logging/monolog_email.rst
+++ b/cookbook/logging/monolog_email.rst
@@ -93,6 +93,13 @@ It then logs everything including messages below the action level.  The
 ``critical`` level is only triggered for 5xx HTTP code errors. The ``handler``
 setting means that the output is then passed onto the ``buffered`` handler.
 
+.. tip::
+
+    When the application crashes with an error 5xx, the swiftmailer memory spool
+    will not be flushed and no mails will be sent. You need to comment out the
+    the ``spool: { type: memory }`` in your ``config.yml`` so the mails will be
+    sent immediately.
+
 .. tip::
 
     If you want both 400 level and 500 level errors to trigger an email,