Update docs

docs/configuration.rst

@@ -62,7 +62,7 @@ there is a good way to disable rate limiting altogether.
 The ``TLS_FLAVOR`` sets how Mailu handles TLS connections. Setting this value to
 ``notls`` will cause Mailu not to server any web content! More on :ref:`tls_flavor`.
 
-The ``TZ`` sets the timezone Mailu will use. The timezone naming convention usually uses a ``Region/City`` format. See `TZ database name`_  for a list of valid timezones This defaults to ``Etc/UTC``
+The ``TZ`` sets the timezone Mailu will use. The timezone naming convention usually uses a ``Region/City`` format. See `TZ database name`_  for a list of valid timezones This defaults to ``Etc/UTC``. Warning: if you are observing different timestamps in your log files you should change your hosts timezone to UTC instead of changing TZ to your local timezone. Using UTC allows easy log correlation with remote MTAs.
 
 .. _`TZ database name`: https://en.wikipedia.org/wiki/List_of_tz_database_time_zones