Message expired for domain message

[XYZdragon]

Hi, I have a client who is having problem with our email domain. Basically, some but not all of the mails he send are getting back to him. The message he gets is the following: Sorry, we were unable to deliver your message to the following address.

<user@domain.com>:
Message expired for domain domain.com

We are able to sent and receive emails, I check DNS/MX record and everything in there seems to be ok. Also, this user is sending the emails from a yahoo business email account and the NDR message is coming from his yahoo domain. There is not indication that the msg are hitting our server at all. Thoughts?

 

[TechyMcSe2k]

First: Make absolutely sure that he is typing your domain correctly.
Second: Try an outside Hotmail, GMail or Yahoo account and verify that you have no issue emailing yourself.
Third: Have him open a troubleshooting case with Yahoo. If he is using Business Email with Yahoo, then he should be able to do this. They don't care about free users