I have a hosted service in Australia on version 8 and we have had a problem develop recently where replying to a message does not move the message to the top of a users inbox.  Also, if a user has ticked a message thread done (so that it is only viewable in the archive) and that message receives a new reply, the message does not get returned to the users inbox.  This means that missing messages is very easy to do.

Is there a configuration setting that could cause this?  We have IT Libertas' module 'No Auto Subscription' (https://www.odoo.com/apps/modules/10.0/compoze_no_auto_subscribe/) installed but uninstalling it does not make any difference.