Even though WP Comment Auth seems to work, I still end up having to “moderate” WordPress comment spam. The Three Strikes plugin works like SpamAssassin to automatically reject comments that score above a certain threshold. I applied couple of hacks noted by others to send notification when a comment is blocked, and also to display the comment before it’s rejected, in case it is in fact legit. Here’s my version of the plugin.
If that is your code, then it won’t track the IP because you’ve made the same mistake as me – the mail should send $user_ip, not $userip.
I like to think my additions that give a clickable search of the WHOIS registries to reverse the IP to find the network it came from are useful.. find them at the TSPlugin comments.