Aol & Exchange 2000

I have setup and exchange 2000 server recently. I’m problem is this. We are unable to sent e-mail to anyone with an AOL address. There is no rejection or no reply back nothing. The message just simply disapears. However we can recieve email from AOL users. We are not listed on the SMTP relay sites. So I’m not sure where the problem lies. This only happens with AOL address’s.