Sure, but that's a different story. You might piss them off and lose customers. You may also be knowingly increasing your support costs. For the average comp

Sure, but that's a different story. You might piss them off and lose customers. You may also be knowingly increasing your support costs. For the average company trying to navigate these sorts of decisions, supporting users with emails like "a$123@1-2-3.12397.museum" probably isn't high on their list of priorities, regardless of whether it's "valid" or not.