[Admin]

You'll need to comment out / delete this code from register.php:

  if ($enablebanning and $banemail!="") {
    if (stristr(" ".$banemail." "," ".$email." ")!="") {
      eval("standarderror(\"".gettemplate("error_banemail")."\");");
      exit;
    }
    if ($emaildomain=substr(strstr($email,"@"),1)) {
      if (stristr(" ".$banemail." "," ".$emaildomain." ")!="") {
        eval("standarderror(\"".gettemplate("error_banemail")."\");");
        exit;
      }
    }
  }

And then do whatever you did.