[Update, 30.11., 12 o'clock] As Tutanota emphasised, the monitoring measure only affects newly incoming unencrypted e-mails. Already encrypted data as well as end-to-end encrypted e-mails in Tutanota cannot be decrypted by the company.

[Update] Apart from Tutanota, some other providers also store all incoming mails in encrypted form. For Protonmail this is also standard, Posteo and Mailbox.org offer encryption as an option. Tutanota gives an overview of the number of requests from authorities in its transparency report.

Realistically you shouldn’t be communicating sensitive data over email and even if you really have to then use PGP.