DNS and email problem

Hello:

I get emails back with this message: (I assume it's coming from our exchange
server, maybe?)

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Your message did not reach some or all of the intended recipients.
Subject: Our company's name
Sent: 3/9/2006 4:24 PM
The following recipient(s) could not be reached:
'macy.fox@xxxxxxxxxxx' on 3/9/2006 4:24 PM
There was a SMTP communication problem with the recipient's email server.
Please contact your system administrator.
<ourcompany.org #5.5.0 smtp;521-EHLO/HELO from sender 70.xx.xx.xxx does not
map to ourcompany.org in DNS>

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What can I do. It looks like there is a DNS problem on our end?
99% of our email is fine though, but this person can't get anything to
comcast and sometimes to aol accounts.


Bryce.


.