Exchange 2010 error Sending to verizon.net

Greetings,
Recently we started getting NDR's from any verizon.net address we send to. Started a about 3 days ago. No other issues sending mail. Below is the NDR we get when sending to any Verizon.net address.

Thanks,
Tim

Diagnostic information for administrators:

Generating server: CHI-CAS-01.chi-sd.com

mmagaw@verizon.net
vms172049pub.verizon.net #500 5.5.1 Unknown command "XXXX 3859 LAST" specified ##rfc822;mmagaw@chichestersd.org

Original message headers:

Received: from Chi-Exchange-01.chi-sd.com ([fe80::85bb:5812:7b16:6258]) by
 Chi-CAS-01.chi-sd.com ([::1]) with mapi id 14.01.0218.012; Mon, 17 Sep 2012
 06:05:31 -0400
From: "McGrath, Tim" <tmcgrath@chichestersd.org>
To: District-Staff <District-Staff@chichestersd.org>
Subject: Home directories and shared drives
Thread-Topic: Home directories and shared drives
Thread-Index: Ac2Uu7lFDmjd5eIvS8SwbW42Hpi5vg==
Importance: high
X-Priority: 1
Date: Mon, 17 Sep 2012 10:05:31 +0000
Message-ID: <981C73450DEA3C4A93A76734C89165442AE6F429@Chi-Exchange-01.chi-sd.com>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-originating-ip: [172.16.0.12]
Content-Type: multipart/alternative;
      boundary="_000_981C73450DEA3C4A93A76734C89165442AE6F429ChiExchange01ch_"
MIME-Version: 1.0
X-Auto-Response-Suppress: DR, OOF, AutoReply