Bouncebacks when sending to sister domain.

I manage two domains.  Both have exchange servers.

When my user tries to send an email from one domain to the other, randomly she will get bouncebacks.  After the bounceback she send again to the same addresses with no problems.

The headers indicate that although she send to user@humboldtwholesale.com, outlook tries to send it to user@house-garden.us, which is the domain she is sending from.   After she gets the bounceback, she can send again to the same address and it goes through.

Here are the headers:

Delivery has failed to these recipients or groups:

Andrew SchellThe email address you entered couldn't be found. Please check the recipient's email address and try to resend the message. If the problem continues, please contact your email admin.

Ward PattersonThe email address you entered couldn't be found. Please check the recipient's email address and try to resend the message. If the problem continues, please contact your email admin.

Diagnostic information for administrators:

Generating server: HG-EX-01.HoGa.local

IMCEAEX-_o=HW-NHS_ou=Exchange+20Administrative+20Group+20+28FYDIBOHF23SPDLT+29_cn=Recipients_cn=Andrew@house-garden.us Remote Server returned '550 5.1.11 RESOLVER.ADR.ExRecipNotFound; Recipient not found by Exchange Legacy encapsulated email address lookup'

IMCEAEX-_o=HW-NHS_ou=Exchange+20Administrative+20Group+20+28FYDIBOHF23SPDLT+29_cn=Recipients_cn=Ward+20Patterson38e@house-garden.us Remote Server returned '550 5.1.11 RESOLVER.ADR.ExRecipNotFound; Recipient not found by Exchange Legacy encapsulated email address lookup'

Original message headers:

Received: from HG-EX-01.HoGa.local (192.168.18.31) by HG-EX-01.HoGa.local

 (192.168.18.31) with Microsoft SMTP Server (version=TLS1_2,

 cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384_P256) id 15.1.845.34; Fri, 13

 Sep 2019 10:10:28 -0700

Received: from HG-EX-01.HoGa.local ([fe80::146f:9222:11f:5e88]) by

 HG-EX-01.HoGa.local ([fe80::146f:9222:11f:5e88%13]) with mapi id

 15.01.0845.039; Fri, 13 Sep 2019 10:10:28 -0700

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

Content-Transfer-Encoding: binary

From: Malorie McCurdy <Malorie@house-garden.us>

To: Seth <seth@humboldtwholesale.com>, Andrew Schell

        <IMCEAEX-_o=HW-NHS_ou=Exchange+20Administrative+20Group+20+28FYDIBOHF23SPDLT+29_cn=Recipients_cn=Andrew@house-garden.us>,

        Ward Patterson

        <IMCEAEX-_o=HW-NHS_ou=Exchange+20Administrative+20Group+20+28FYDIBOHF23SPDLT+29_cn=Recipients_cn=Ward+20Patterson38e@house-garden.us>

CC: "'Eric Weems (eric@humboldtwholesale.com)'" <eric@humboldtwholesale.com>

Subject: Exotic Genetics - Emerald Cup 

Thread-Topic: Exotic Genetics - Emerald Cup 

Thread-Index: AdVqVMRLTSf+I05qTTeux+caAvZr0w==

Date: Fri, 13 Sep 2019 10:10:28 -0700

Message-ID: <94a15fd7964a4ab59b6bd9ef474291e8@house-garden.us>

Accept-Language: en-US

Content-Language: en-US

X-MS-Has-Attach:

X-MS-TNEF-Correlator: <94a15fd7964a4ab59b6bd9ef474291e8@house-garden.us>

MIME-Version: 1.0

X-Originating-IP: [192.168.18.90]

Return-Path: Malorie@house-garden.us