we install new mail server with with smartermail free gateway server and we are migrating domains one by one to our smartermail server.

all the websites hosted in rackspace and it related to travel operation so all the booking related mail sending through this 3rd party smtp host smtp2go(smtpcorp) authenticated account so they confirm each and every mail delivery to costumer mail boxes but all the mails receiving from this web server through smtpcorp to our server getting below error

-----Original Message-----
From: System Administrator
Sent: Tuesday, 5 January, 2016 03:59
To: enxxx@mabuhaytravel.co.uk
Subject: Delivery Failure

Could not deliver message to the following recipient(s):

Failed Recipient: conxxx@mabuhaytravel.co.uk
Reason: Remote host said: 550 Authentication is required for relay

-- The header and top 20 lines of the message follows --

Received: from gate.forward.smtp.iad3a.emailsrvr.com (gate.forward.smtp.iad3a.emailsrvr.com [204.232.172.40]) by MailEdge01.mabuhaytravel.co.uk with SMTP;
Mon, 4 Jan 2016 19:59:25 -0800
Return-Path: <enxxx@mabuhaytravel.co.uk>
X-Spam-Threshold: 95
X-Spam-Score: 0
X-Spam-Flag: NO
X-Virus-Scanned: OK
Authentication-Results: smtp11.gate.iad3a.rsapps.net header.DKIM-Signature=@smtpcorp.com; dkim=pass
X-MessageSniffer-Scan-Result: 0
X-MessageSniffer-Rules: 0-0-0-2945-c
X-CMAE-Scan-Result: 0
X-CNFS-Analysis: v=2.1 cv=IvInLtPg c=1 sm=0 tr=0 a=JWuGvDRtfE5H3m2vv7NRDg==:117 a=JWuGvDRtfE5H3m2vv7NRDg==:17 a=L9H7d07YOLsA:10 a=9cW_t1CCXrUA:10 a=s5jvgZ67dGcA:10 a=hMgq8R9AAAAA:8 a=mD95u9NkAAAA:8 a=kj9zAlcOel0A:10 a=3DwXih_bWBFMlAarP_wA:9 a=y-ecAZeJ--Ih2UrT:21 a=eyU3lFpbL3MUcy-H:21 a=CjuIK1q_8ugA:10
X-Orig-To: fares@tcukmail.co.uk
X-Originating-Ip: [216.22.15.50]
Received: from [216.22.15.50] ([216.22.15.50:36448] helo=a0i218.smtpcorp.com)
by smtp11.gate.iad3a.rsapps.net (envelope-from <enxxx@mabuhaytravel.co.uk>)
(ecelerity 2.2.3.49 r(42060/42061)) with ESMTPS (cipher=AES128-SHA)
id 79/7D-23214-89F3B865; Mon, 04 Jan 2016 22:59:20 -0500

 
We have asked the 3 party service if they are sending mail from a static IP, and so they provide us all the ip ranges
and we enter those to by pass authentication list in the smartermail but still no hope
 
How do we solved this