It’s just a general rule of thumb: privacy and security companies can work well against outside attacks but can only do so much against a government/court order, so don’t expect any of them, not even Mullvad, to go to jail for you. Encryption, anonymization and no logging are the most anyone can expect/hope for from a company, which still puts companies like Proton or even Tutanota leagues ahead of the spyware that is Gmail, Yahoo or Microsoft when it comes to email. The end user needs to do the rest themselves.