Please. Captcha by default. Email domain filters. Auto-block federation from servers that don’t respect. By default. Urgent.
And yes, to refute some comments, this publication is being upvoted by bots. A single computer was needed, not “thousands of dollars” spent.
There’s one exception to that. If you originally created the email address with a dot in it, as in, signed up for gmail as “hello.2@gmail.com,” it’s treated as a literal character in the username portion and is required.