The accepted solution is to have a constitution that says otherwise.
Which is a bit complicated here, as the EU has no real constitution and this 'law' (really a regulation) is a blatant violation of the constitutions of countries that did choose to establish secrecy of correspondence.
Which is a bit complicated here, as the EU has no real constitution and this 'law' (really a regulation) is a blatant violation of the constitutions of countries that did choose to establish secrecy of correspondence.