That IP address 64.12.102.137 belongs to AOL in the USA and is currently on two blacklists
see
Network Tools: DNS,IP,Email
if you plug the IP address into this engine you also get two positive hits
Blacklist Check
Presumably Hotmail check against one of these
What can you do?
1) get AOL to do something about clearing the records
2) try to get the records cleared yourself by online requests to the listing companies
3) switch AOL servers. Are you using webmail or pop/imap?
If pop/imap switch to pop.aim.com (or imap.aim.com) and smtp.aim.com
It sometimes works switching to the AOL UK Talktalk servers (but I can't remember those offhand)
Or pushing it even further for outgoing mail try the authenticated server: smtp.aim.com on port 587
totally pointless calling Microsoft / Hotmail. They won't have the freedom to override the blocklist. Only AOL or the list providers can do that
Edit
Just a PS to say my AOL accounts (most of which originated as Netscape accounts) are all routed through the authenticated AIM server and I have no problems sending to Hotmail