It is constantly blocking proxies, Tor nodes, and a bunch of IP ranges from various list files. It’s actually up. I’ve been fooled into thinking it’s down too. Given your email provider isn’t blocked, you can mail admin at that domain and ask which list it is for you, in my case I was able to trace it all the way back to someone spamming a forum.

One thing I learned pretty recently is that this “privacy” service actually has a privacy frontend for it: s/c/f (catbox.moe > fatbox.moe) (read only).