@bdistler: That's a funny macro you've got there about checking IP's
However, my own IP has little to do with a server returning a 403. That only hints at a missing default index and also a missing default 404. I've read through some other related posts and that brought me to run a test against my own site, which as of recently has never been associated with spam in any way. Sadly, the shared IP it was assigned by x10 DNS appears on not one, not two, but three black-lists. Hm...
I understand there is always a risk with free hosting, but sure enough there are also plenty of mechanisms to fight back. Sorry if this reads like hijacking someone elses thread, but I'd very much appreciate if either you, or a qualified admin with sufficient rights could have a look into the matter and post back, thank you.