The European Court of Human Rights recently ruled that an employee's communication may not be monitored without prior notice and without specific reasons. [1]

This ruling applies not only to the whole EU, but to the 47 member states of the Council of European, including for example Russia and Turkey.

[1] https://www.coe.int/en/web/human-rights-rule-of-law/-/echr-m...

Requiring approval of the worker's council is how an employer's demand to read an employee's mail is usually handled in Germany. I did not mean to imply that it is handled the same way in the whole EU, just that unsubstantiated monitoring is likely illegal in the whole EU.