Problems Receiving Email to Alternate Domains In Exchange

My exchange server is rejecting email sent to valid addresses withing my orginization.

smtp.mydomain.com's postmaster response:
>>> RCPT TO:<user@myotherdomain.com>
<<< 550 5.7.1 Unable to relay for user@myotherdomain.com
smtp.mybackup.com's postmaster response:
>>> RCPT TO:<user@myotherdomain.com>
<<< 550 User unknown

I have double checked all settings on exchange. Things were working last week.
LVL 5
ekleinerAsked:
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ekleinerAuthor Commented:
This is an automatically generated Delivery Status Notification

Delivery to the following recipient failed permanently:

    user@myotherdomain.com

Technical details of permanent failure:
PERM_FAILURE: SMTP Error (state 9): 550 5.7.1 Unable to relay for user@myotherdomain.com

  ----- Original message -----


Received: by *.*.*.*with SMTP id *************************
Mon, 19 Mar 2007 08:37:27 -0700 (PDT)
Received: by *.*.*.*with HTTP; Mon, 19 Mar 2007 08:37:27 -0700 (PDT)
Message-ID: <***************************************@mail.gmail.com>
Date: Mon, 19 Mar 2007 11:37:27 -0400
From: "outsideemail" <me@gmail.com>
To: user@myotherdomain.com

Subject: Test inst
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
0
LeeDerbyshireCommented:
If you're sure you've double-checked everything, then it will be hard to suggest something.  However, the first thing I would check is that the second domain is still in your Default Recipient Policy.
0

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