With the web interface, it's possible to receive notifications. Using GNOME Shell 3.22.3 with Firefox 51.0.1 (64 bits) on Fedora 25, begin of messages actually appear on the top of the screen for a brief moment when they are received. Usually, one might then click on the notification stack panel widget, and have a list of recent unread messages. This messages are then activable (clickable), which usually focus the relevant window. But Mattermost webinterface messages doen't appear on this stack.
Might I lake some software component, or is this due to a limitation in the web interface?