Email problems

I have a customer that is getting the following error when he sends us an email:

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

  steve@carmichaelengineering.com
    The mail server could not deliver mail to
steve@carmichaelengineering.com.  The account or domain may not exist, they
may be blacklisted, or missing the proper dns entries.

I ran a test from dnsright.com on the email address, see below.

Results from Test Email Address:
Please Wait....

You entered: steve@carmichaelengineering.com
Testing SMTP Server:  65.254.254.50220 impinc02.yourhostingaccount.com NO UCE ESMTP server ready
ehlo DNSRight.com250-impinc02.yourhostingaccount.com hello [66.240.236.220], pleased to meet you
250-HELP
250-SIZE 34603008
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-8BITMIME
250 OK
mail from:250 2.1.0  sender ok
rcpt to:250 2.1.5  recipient ok
221 2.0.0 impinc02.yourhostingaccount.com NO UCE closing connection
Got 250 response, 65.254.254.50 is accepting email got the domain carmichaelengineering.com.

The address is not blacklisted and I can't find any problems with my DNS entries. Can anyone please give me some insight on what I can do to fix this problem even if it is not on my end.