Unknown address error 550-'5.1.1

Zoho,

We have once client (SunTurst) that can not send to this email address ( hamilton@advancedmicrowave.com) Everyone else can sent to hamilton but not SunTrust.

Any help is appreciated..

Thank You

Scott

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Diagnostic information for administrators:

Generating server: mx5.suntrust.com

hamilton@advancedmicrowave.com
[165.254.168.50] #<[165.254.168.50] #5.0.0 smtp; 5.1.0 - Unknown address error 550-'5.1.1 <hamilton@advancedmicrowave.com>... User unknown' (delivery attempts: 0)> #SMTP#

Original message headers:

X-IronPort-AV: E=Sophos;i="5.17,454,1437451200";
d="scan'208,217";a="196801917"
X-IronPort-DK-Sig: SunTrust_com
X-IronPort-DK-Sig: Suntrust
Received: from unknown (HELO GA016E0HT02.corp.suntrust.com) ([10.4.78.44]) by
ga016a0cn.suntrust.com with ESMTP; 02 Sep 2015 12:19:34 -0400
Received: from GA016E0MB10.corp.suntrust.com ([fe80::f88f:f99c:a021:3178]) by
GA016E0HT02.corp.suntrust.com ([::1]) with mapi id 14.03.0248.002; Wed, 2 Sep
2015 12:19:34 -0400
From: Atkins.Kevin <Kevin.Atkins@SunTrust.com>
To: "hamilton@advancedmicrowave.com" <hamilton@advancedmicrowave.com>
Subject: FW: Advanced Microwave
Thread-Topic: Advanced Microwave
Thread-Index: AdDleuN103/1FIMfRouJqinnrkJNfAAIC2Cw
Date: Wed, 2 Sep 2015 16:19:34 +0000
Message-ID: <01ECEE749C215E44B1FC0D7FF630842E35FCD803@GA016E0MB10.corp.suntrust.com>
References: <01ECEE749C215E44B1FC0D7FF630842E35FCD754@GA016E0MB10.corp.suntrust.com>
In-Reply-To: <01ECEE749C215E44B1FC0D7FF630842E35FCD754@GA016E0MB10.corp.suntrust.com>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-originating-ip: [10.4.78.246]
Content-Type: text/plain
MIME-Version: 1.0