There was a court case here a while ago because the feds wanted access to someone's emails. They won the case and forced tuta to build them a way into their system that allows them to get at non end to end encrypted emails before they get at-rest-encrypted. German article https://www.heise.de/news/Gericht-zwingt-Mailprovider-Tutano... English article about the same topic https://hackread.com/encrypted-email-provider-tutanota-backd... This essentially means they are forced to save a copy of the non encrypted emails somewhere, at least for german customers. You can argue its not a "backdoor" in the typical sense, since end to end encryption is still in place, but like, come on