IP and email banning is also a whack a mole, ISP's and network range from actively maintained global blacklists is much, much more effective. That and also heuristics which I'm not sure this forum software has it.Any system that uses an IP address as an identifier to ban is a waste of time so to speak...Its not hard to acquire a new IP address if you wanted one even if youre in the same location...People do this all the time on game sites to cheat or after being banned for cheating or breaking the rules.
I havent been on one site that doesnt get some form of spam.