It looks like the IP (or IP range) for my dedicated server is blacklisted for Spam.
I don't believe anything has been hacked and there's spam coming from it. How can I properly check? It's getting annoying seeing my access banned in places, especially forums, when I'm browsing via the server via a socks proxy.
Is anyone in your household from Nigeria?
Is this paid for hosting or a server hosted at home? Check firewall, use it to block outgoing ports as well as incoming. You can also use tools like ntop to check network traffic into and out of the box. If you're not sure, wipe it and reinstall and secure it again.
If you're confident it's not been hacked, ask for a different IP outside of the affected block.
It's my dedicated server from OVH. I'll do some checking to see if there's anything dodgy.