Hi, sorry, should have updated this a few days ago.
Basically, I did all the jumping through hoops and cartwheels and whatnot that Microsoft demand to get my domain unblocked. There's no one to talk to, no customer service people, you just have to follow some instructions from the Microsoft website, which basically says to register the domain on two separate sites, and try to prevent whatever they object to, happening (no advice on how to find out what that is).
I surmised that, as I host arouind 70 forums on the forumlaunch site (and though I use Offtopica2.com as a domain name here it's still hosted with forumlaunch; just type
http://offtopica2.forumlaunch.net in your address bar and it'll send you here), the probem was with fake spam accounts trying to register with false hotmail addresses. As you know, when you register you get an activation email with a link to activate your account. So, hotmail were receiving loads of registration emails to hotmail accounts that didn't exist (70-odd forums generates a hell of a lot of that) from my domain, hence the blacklisting.
Anyway, did the required stuff Microsoft demand, and manually updated anti-spam measures on every forum I host (hours upon hours of tedious work). Then crossed my fingers. As I said, no customer service, no one to talk to, from Microsoft. And, it seems, no notification of success.
So it was with great relief last week that I discovered that people with hotmail email addresses were able to register without any problem. Which is great news for me, and my hosting business, as well as any of you who have hotmail email addresses.
Sorry for the length of this post. The long and the short of it is that there is now no problem with hotmail email addresses, and I'm going to lock the threead.

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White collar conservative flashin' down the street
Pointin' their plastic finger at me. Ha!
They're hopin' soon my kind will drop and die but, uh,
I'm gonna wave my freak flag high. HIGH!