In fact, knowing that the only thing Proton was able to hand over was the credit card identifier is pretty solid proof that they in fact cannot access (and thus provide access to) your email account and its contents.
If full anonimity is the goal then stick to crypto or cash payments, because credit card always leaves a trail and not a single email provider is above the law in that regard.
This case is entirely the fault of the user’s bad opsec.
In fact, knowing that the only thing Proton was able to hand over was the credit card identifier is pretty solid proof that they in fact cannot access (and thus provide access to) your email account and its contents.
If full anonimity is the goal then stick to crypto or cash payments, because credit card always leaves a trail and not a single email provider is above the law in that regard.
This case is entirely the fault of the user’s bad opsec.