Re: I am not surprised
Welcome to El Reg; the home of cynical sysadmins the world around and congratulations on your first two posts.
Do you actually individually check the IP for each and every email you've ever received and if it's spamming or not? Because I have to say that running my own spam filter myself that appears like an immensely huge amount of work to go through and find all emails from a particular IP range and then determine that they are all spam, as that's going to have to be done manually and banning IP ranges is always subject to a high level of false positives.
What tools did you use to do the checking?