Not enough info to help.
I'd need to know his e-mail address to see if that's the problem and likely his IP address as well. I can get around the issue of our server thinking he is a spammer but not without enough info to check into why it says so.
I checked and his username there isn't on the stop forum spam list but see no way to check his e-mail there and for sure not his IP as that is blocked on all sites other than to mods and admins.
