I have a forum and there is a troll. He comes back with a new isp every five minutes. Can i stop this by having their email when regestring? I guess he could create a new email in seconds, so what can i do?
If there is no constant that you can trace then - apart from it driving you nuts and doing as Stuartli suggests I don't think there is anything you can do other than deleting the troll posts until the troll eventually gets fed up of being ignored and goes away to pester someone else.