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.
Email domain filtering makes no sense when it is easy enough to just set up your own email server for bots. It will only hinder legit users and low level bad actors, not the real threat of major bot farms.