Sending email to AOL customers can be a tricky business. Especially if you are say running your own mail server on an ISP connection like a lot of small businesses do, typically with Exchange on Windows 2003 Small Business Server.

AOL have given one minor tool to help you avoid the bouncebacks, (typically by changing your configuration so your email is sent through another SMTP 'smarthost' like an ISP's SMTP server)

Once you've made changes that you think are needed, you can test the outgoing IP by emailing to the AOL IP Confirmation email ipconfirm@mailtest.mx.aol.com