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.
Ahh, yea that's right. Regardless, just all the more reason that it's kind of silly to do what OP is talking about. Sure, you could filter out the + signs as well but overall it's a pretty pointless implementation.