On November 27th AOL started experiencing an incident impacting their ability to receive mail. As a result, messages sent to AOL addresses are delayed and may eventually return the bounce message. AOL is investigating the issue, and we will update this article once AOL has resolved the incident. Note that if you receive a bounce notification, the email will need to be resent to those addresses once the issue has been resolved.

UPDATE: On November 30th, AOL resolved this particular behavior. Please resend emails to an AOL email addresses that bounced.