If you pay Proton Mail for a service, they may hand over the payment data in response to a court order: https://www.404media.co/proton-mail-helped-fbi-unmask-anonymous-stop-cop-city-protestor/
Proton Mail Helped FBI Unmask Anonymous ‘Stop Cop City’ Protester

A court record reviewed by 404 Media shows privacy-focused email provider Proton Mail handed over payment data related to a Stop Cop City email account to the Swiss government, which handed it to the FBI.

404 Media
@evacide I've been following the articles on this, and was curious -- you would know this better than I -- does it sound like they were in a position where they had a legal alternative?

@cliffle @evacide All companies have to comply with the jurisdiction in which they are registered. In this case they complied with Swiss law, not the FBI directly, so the headline seems a bit misleading.

The takeaway is: If you pay for any service in a traceable way, you are not anonymous. If you want to be anonymous, consider cash or Monero.