How to help a buyer whose email ID returns failed delivery?

Is there any possible way to give support to a buyer whose email ID returned failed delivery? He sent me an email now and I usually respond fast but when I replied him, it will return “Delivery to the following recipients failed.” Any quick solution to this?

Thank you my friends.

EDIT : Quite surprising that someone will email you and when you respond back, the message will not be delivered. I guess there is something wrong with this buyer’s email ID – although, he was able to successfully email me through my profile.

some email server have strange filters (firewalls) so it could be your email is being prevented by a firewall. *Maybe

EDIT : try using well know emails like, yahoo, or gmail …

My official email for this marketplace is hotmail. The problem is from the end of the buyer. I am afraid whenever I am unable to support my buyer on time. Wish he is in this forum now to email me with a different email ID because I have verified his purchase.