Exchange not able to send to AOL

My exchange server is not able to send email to AOL.COM. My users are able to receive email from AOL. When email is sent to AOL, it goes in the outbound mail queue and then leaves. But the AOL recipient receives no email. The event logs on the Exchange server say “a new SMTP connection has been made to host 205.188.156.164(for AOL.COM).” I need to find a solution for this. The person who provides the right solution will get all the points.