SMTP problems from *.ipt.aol.com

I have several users who connect to our mail server from an IP in the *.ipt.aol.com namespace. All are complaining about intermittent SMTP problems. I see that outbound SMTP traffic is proxied through AOL servers to our mail servers. Has there been a change recently causing this to not work? Our mail server does a name lookup on the IP and every once in awhile this will fail. Im assuming AOL DNS servers stop answering queries occassionally? Any ideas much appreciated. -- Aj. Sys. Admin / Developer