Exchange 2010 – Delivery is delayed to these recipients or groups

Hello everyone!
A few days back I got Exchange 2010 installed. Since then I have been being failed to send any emails to a particular domain. I couldn't figure out what is wrong with me. My assumption is that the problem lies with aol.com.
While sending emails I am getting the following message,
Delivery is delayed to these recipients or groups:
*******@aol.com
Do you have any idea? Please let me get of this garbage asap.
Thanks in advance.
