This message was created automatically by mail delivery software.

 A message that you sent could not be delivered to one or more of its recipients. This is a permanent error.

xxx@xxx.xxx Invalid Address, ERROR_CODE :550, ERROR_CODE :5.1.1 <xxx@xxx.xxx> recipient rejected

  Return-Path:< x xxx@xxxxx.xxxx >

 Received:from x.x.x (x.x.x [000.000.000.000) by mx.zohomail.com

      with SMTP id 1388782244541749.1237443292866; Fri, 3 Jan 2014 12:50:44 -0800 (PST)  Message-ID:<84FAAD8507696C4F93FADE7914BC20D9083FCB75@xxxx.xxxx.xxxxx>

 Date:Fri, 3 Jan 2014 20:50:42 +0000

 From:"xxxxxx" <xxxxx@xxxxx.com>  To:"xxxxx@xxxxx.us" <xxxxx@xxxxxx.us>  Subject:test  Content-Type:multipart/alternative;

      boundary="_000_84FAAD8507696C4F93FADE7914BC20D9083FCB75_"

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I have only two MX records pointing to mx & mx2.zohomail.com.  Other zone file entries include a rsa domain key and a validation alias.

I receive the same error no matter what mailbox I send to in my domain.