To add to that, they are very open about inquiries from legal authorities, see their yearly Transparency Reports:

Not all the enquiries we receive are legal, and our data protection officer will critically assess every single request in order to make sure it is in line with the requirements of the law. If there are any doubts about the legality of a request, our specialised lawyers will be consulted. If a request is formally and legally correct, we will service it, otherwise it will be rejected.

…BUT E-Mail is an insecure form of communication by default, so you should definitely look into PGP encryption, see Privacy Guides - Email Security.