552 Message exceeds fixed maximum message size

After reviewing all of the posts on this issue we are still not able to resolve our issue.
Users limit is set to 50mb
Receive Connector is set to 200mb
Max Header Size is set to 128kb - Changed from default 64k

A specific domain sends a message that is 13mb and exchange returns it due to the message exceeding fixed maximum message size.

This same domain can send the message to gmail and my user then sends that message to themselves at our organization and is able to receive it just fine.
From: Mygateway
To: user@externaldomain.com
Reply-To: <>
Subject: Delivery Notification <user@mydomain.net>
Date: Thu, 10 Jun 2010 11:15:57 -0500
MIME-Version: 1.0
Content-type: multipart/report;
report-type=delivery-status;


This is a multi-part message in MIME format.


Content-Type: text/plain;
charset="us-ascii"
Content-Transfer-Encoding: 7bit
This is a delivery status notification, automatically generated by MTA mygateway.mydomain.net on Thu, 10 Jun 2010 11:15:57 -0500
Regarding recipient(s) : user@mydomain.net
Delivery status : Failed. Message could not be delivered to domain <mydomain.net> .Failed to accept the sender.
MTA Response :552
The original message is included as attachment.

--C-I-P-H-E-R-T-R-U-S-T-1276186557.642296
Content-Type: message/delivery-status;
charset="us-ascii"
Content-Transfer-Encoding: 7bit

Reporting-MTA: dns; emailgateway.mydomain.net

Final-Recipient: rfc822;user@mydomain.net
Diagnostic-Code: smtp; 552 Message exceeds fixed maximum message size
Remote-MTA: dns; 10.1.0.60 (Email Server IP)
Action: failed
Status: 5.0.0