You can block mail in both the AOL software and webmail. If you are using version 9.1, log in and go to Keyword "Mail Controls." Once there click on "Sender Filter." You'll be offered a number of options by which you can block or allow emails based on the sender's address.
In webmail log in and go into "Settings." Under the "Spam Controls" section you'll be offered a number of options by which you can block or allow emails based on the sender's address.
Senders who are blocked by spam controls will receive a message back indicating that the recipient is not accepting email from the sender's address.