#550 5.1.1 RESOLVER.ADR.RecipNotFound; not found ##

I am having trouble with one user email intermittently sending bounce back messages to users regardless of user domain.  This occurs both in our company domain and outside the company domain.  The primary exchange email address is gottsch.net, this user is using the cattlexpert.com email address, but the issue is across both email domains.  I have also created a new alias in the cattlexpert.com domain, but the issue happens with that address as well.  We can send email one minute and it gets to his mailbox without incident, and the next minute, we can try and send email but will receive a bounce back undeliverable message from our exchange server like the one below:

Delivery has failed to these recipients or distribution lists:

Scott Moore The recipient's e-mail address was not found in the recipient's e-mail system. Microsoft Exchange will not try to redeliver this message for you. Please check the e-mail address and try resending this message, or provide the following diagnostic text to your system administrator.

Sent by Microsoft Exchange Server 2007

Diagnostic information for administrators:

Generating server: elks12.Gottsch.local

scott@cattlexpert.com #550 5.1.1 RESOLVER.ADR.RecipNotFound; not found ##

Original message headers:

Received: from elks12.Gottsch.local ([10.2.1.12]) by elks12.Gottsch.local

 ([10.2.1.12]) with mapi; Tue, 14 Oct 2014 15:55:23 -0500

Content-Type: application/ms-tnef; name="winmail.dat"

Content-Transfer-Encoding: binary

From: Ryan Lynch - CattleXpert <ryan@cattlexpert.com>

To: Courtney Cale <courtney@kansascattlemen.com>

CC: Scott Moore <scott@cattlexpert.com>

Date: Tue, 14 Oct 2014 15:55:21 -0500

Subject: RE: Special Edition Ad

Thread-Topic: Special Edition Ad

Thread-Index: AQKbF50zuV8iHXI28209NI08o9S9sQDSPc5lmpMULTCAAAzl0A==

Message-ID: <78016C64357C7043B59A839139A7EE810141DE0C7AA3@elks12.Gottsch.local>

References: <!&!AAAAAAAAAAAYAAAAAAAAAECdAh4yaAFDq2W2mcZT20bCgAAAEAAAAFeLLBqimDxMidO94ZtU5zMBAAAAAA==@kansascattlemen.com>

<78016C64357C7043B59A839139A7EE810141DE0C7A8E@elks12.Gottsch.local>

<001e01cfe7ea$ce8945a0$6b9bd0e0$@kansascattlemen.com>

In-Reply-To: <001e01cfe7ea$ce8945a0$6b9bd0e0$@kansascattlemen.com>

Accept-Language: en-US

Content-Language: en-US

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X-MS-TNEF-Correlator: <78016C64357C7043B59A839139A7EE810141DE0C7AA3@elks12.Gottsch.local>

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