AOL SMTP Response Code
Some AOL mailers are experiencing a new SMTP Response code from remote mail servers:
521 5.2.1 : AOL will not accept delivery of this message.
If you’re seeing this response code, please double check your System > Bounce Cleaner page from the Admin UI.
Verify that Volo is setup to detect a rule and assign a bcount value of 0 if you’d like you’d like to disregard this bounce.
For any questions, please email email@example.com or firstname.lastname@example.org