Hacker-X writes "According to this item over at Spam Kings,
AOL has had a large swath of its IP addresses added to the Mail Abuse Prevention Systems (MAPS) Real-time Blackhole List (RBL).
The RBL is used by many corporations and large ISPs to filter spam.
MAPS evidently started blocking the AOL mail servers less than 24 hours after filing a complaint with AOL's abuse desk. The block was initiated in response to spam emanating from AOL mail servers."