Do you use the Messages Block in your Moodle courses? Be advised it will disappear!
From Moodle 3.4 the Messages Block will disappear, because the Messaging system in Moodle is now far more integrated, and in most Themes messages are available from the menu.
Admins can read the Tracker item here: https://tracker.moodle.org/browse/MDL-57115
The good news for administrators is that the Messages Block is automatically deleted during the upgrade to Moodle 3.4, so there is nothing extra required.
However, if you have teachers using courses with the Messaging Block, it’s definitely worth explaining that this will be removed from their courses when you upgrade to Moodle 3.4.