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.
This is not "gmails" behavior. This is called "verb" and it is one of the best things ever. I only use verb for signing up at stuff. So, i can sort, and know when someone misuses my mail address.
And, if i would need to create an alt, to post stuff, that i don't want somebody do bring in connection with me (TIFU, NSFW, whatever you like) i would use verb.