553 errors

[Shannon @ shaw]

I have several people that tell me they can't send mail to me (in this 
example case, my-user at my-xyz.com)
Usually I have a hard time getting them to forward me the errors or maybe I 
don't even hear about it because I just didn't know anyone was e-mailing me.
This one lady (her-user at her-xyz.com) however was able to forward me the 
error message.
It looks like her company uses google to forward mail and my server is 
rejecting it.
Do I have something mis-configured here? Do I have to make an exception to 
allow google as a relay?

I've changed the sender and recipient addresses but it basically looks like 
this:


Delivery to the following recipient failed permanently:

     my-user at my-xyz.com

Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the server for
the recipient domain my-xyz.com by mail.my-xyz.com.
[111.111.111.163].

The error that the other server returned was:
553 5.3.0


----- Original message -----

DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=her-xyz.com; s=google;
        h=from:references:in-reply-to:mime-version:thread-index:date
         :message-id:subject:to;
        <encrypted nonsense>
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=1e100.net; s=20130820;
        h=x-gm-message-state:from:references:in-reply-to:mime-version
         :thread-index:date:message-id:subject:to;
        <encrypted nonsense>

X-Gm-Message-State:
AA6/9RkHXkTbYI6xmMt6xu2tQHQz3YeuuvipfbFY/monaFJUKJtQA7PKgREYvFNyCEJ4ot9hr0HGz+EtgeRMvSwF
X-Received: by 10.107.34.144 with SMTP id
i138mr6826088ioi.197.1476889626314;
Wed, 19 Oct 2016 08:07:06 -0700 (PDT)
From: Her User <her-user at her-xyz.com>
References: <935487A50EDE4DCB860487590C80C169 at VCMCE110228>
In-Reply-To: <935487A50EDE4DCB860487590C80C169 at VCMCE110228>
MIME-Version: 1.0
X-Mailer: Microsoft Outlook 16.0
Thread-Index: AQKYoSoKkLEFwHXxnMVCPGibF3LCz58i8nWw
Date: Wed, 19 Oct 2016 10:06:46 -0500
Message-ID: <559fbc8415e1e417c7d7ff2ae1880485 at mail.gmail.com>
Subject: RE: a few more
To: My User <my-user at my-xyz.com>
Content-Type: multipart/alternative; boundary=001a1140a10c8cc6d2053f392931

Thank you Mr. User!