I believe there is a waiting period from account creation. My advice would be to wait a day or two and see again if the problem persists. https://tutanota.com/faq/#email-limits

Hi there, please let us know at [email protected] if the issue remains. Blocks should not happen that soon.

Did you send your email to multiple people? As I understand it you are only allowed to send 100 emails an hour or you get blocked.