The university where I work switched to Moodle version 3.6 last July and the messaging function was not unanimously accepted. In fact, the biggest problem comes from the fact that it is not possible to select conversations in order to be able to delete them all in one action.
The only way right now is to click to read the conversation, then click on the three small dots and click on delete.
However, a teacher can receive about a hundred messages in a single semester. Is there a way to only select all received messages and delete them (like a mailbox)?