Even this regexp has false positives. The `ai` ccTLD ran their own mail server at the root, so an address like `a@ai` was a valid email address. They serve a

Even this regexp has false positives. The `ai` ccTLD ran their own mail server at the root, so an address like `a@ai` was a valid email address. They serve a website at the tld root: http://ai./ http://ai./