I too reported this issue here and an AOL postmaster contacted me offlist and got our servers sorted. On Fri, 11 Dec 2015 15:54:13 -0600 Blake Hudson <blake@ispn.net> wrote:
Aaron, I reported an issue here almost a month ago (521 5.2.1 : AOL will not accept delivery of this message). AOL support did, eventually, acknowledge an issue and the failed deliveries did, eventually, clear up for us. AOL support never stated what the issue was nor did they provide any explanation. The responses that we received, much like the response you received, did not give me the impression that their support staff was provided any information to pass along.
The only advice I can offer is to take care of your own stuff and keep following up with AOL occasionally regarding their issues. There's not much you can do, as a non AOL customer, to resolve their issue. We did have some AOL customers reach out to AOL and it seems as though they also had trouble getting any reasonable level of support.
--Blake
Hough, Aaron wrote on 12/11/2015 11:12 AM:
The following problem has been acknowledged and yet, has been persisting for weeks unfortunately:
"Apparently, email messages ( that with the @aol.com domain ) bounces to and in some occasions, from multiple domains and comes up with Error 521. This has been escalated already. As of writing, we are still working towards a possible solution on this. We would like to apologize for the inconvenience this issue might have caused, but let us assure you that higher level technicians have been assigned to getting this resolved."
-- John PGP Public Key: 412934AC