A public European school has an IT department with a person responsible for all mail related tasks, including the mail server.
Once that responsible sent an incriminatory email to a specific group of teachers, that use email accounts where the content is stored in the school mail server.
One of the teachers from the target group replied. From the content of the reply one can see what the responsible said initially is nonsense.
Then, the responsible deleted all the emails initially sent.
Is this allowed?