The following message to <[removed][at]aol.com> was undeliverable.
The reason for the problem:
5.1.0 - Unknown address error 521-'5.2.1 : (CON:B1) http://postmaster.info.aol.com/errors/554conb1.html'
If you go to the URL, you'll see that the 500-level "CON:B1" status translates to:
"The IP address has been blocked due to a spike in unfavorable e-mail statistics."
Email_Support! You now need to make nice with the AOL Postmaster department (they have procedures, as I'm sure you're aware). Please do so ASAP, as I have more people with AOL addresses with whom I need to communicate than Hotmail/MSN addresses.
Edited by DavidT, 12 September 2012 - 01:13 PM.