Exchange server 5.5 and aol.com mails

HI I am having issue with sending mails to aol.com accounts. All other internet mails are fine but when I send it to an address that has aol.com email it will not get to the person, If I look at the sent items it is gone out of it but I don’t get any bounce back messages or any notifications. Can anyone help me with that????
Thanks in Advance
Alex
alex127@optonline.net