We thank our users for informing us about this bug. Even though we test dozens of browsers before releasing a new version of Tutanota, it is simply impossible due to the endless number of different system versions and browser versions to test everything.
We have now fixed the bug where emails in the Tutanota mailbox were not readable in some browsers. As your browser will automatically re-load Tutanota upon your next login, we inform about every update on our blog. This makes the update-process very transparent to you and increases your security.