Email verification is far from the perfect solution. I've run a website that has user registration for a number of years now. I found that so many bots could successfully respond to email verification that I eventually just turned verification off. Analyzing the registrations, I found that it was actual legitimate users that were the ones having trouble responding to the verification emails, either because of their junk folder rules, they were too lazy to complete the registration, or they used fake email addresses.
What solved the spam problem for me was a plugin I installed that uses 5 different sources to block spam registrations. I believe it uses blacklists, but it's been so long since I installed it, I don't even remember anymore (over two years ago). I still get new users registering and the odd bot from time-to-time, but nothing I can't handle. The plug-in has been a godsend. I suppose it's possible that legitimate users might get caught up in the net, but that might be a risk worth taking as the spam here is really bad.
As for the plug-in I use, I don't run the same platform that's used here, so it wouldn't apply. But I'm sure a popular platform like vbulletin has similar tools (I'm assuming this is a vbulletin forum, as it looks like one).