Very high X-Spam-Threshold when sending email through iis SMTP

Question

I am trying to send email through SMTP configured on server 2003 over IIS 6 but I am getting X-Spam-Threshold value is 95 and I guess due to this some of my customers are not getting their emails. Following steps I have performed.

1. Created new SMTP virtual host
2. List item and specify domain name for which I want to send email.
3. Grant connection to local ip address (10.8.1.100).
4. Relay allow everyone by choosing option "All except the list below" and keep list empty.
5. In Access >> Authentication I have keep "Anonymous Access" checked since I am restricting port at firewall so noone can access it from outside.
6. Message size keep around 20 MB (this is the reason I am using local IIS SMTP service to send email).

I have already have SPF record added for my server public IP address. And below header I receive for email send through. Any help will be appreciated.

Return-Path: <donotreply@xxx.xxx>
Delivered-To: pritesh@xxx.xxx
Received: from smtp10.gate.ord1b (smtp10.gate.ord1b.xxx.xxx [10.130.68.10])
    by store70a.mail.ord1a (SMTP Server) with ESMTP id B2B2E2A00FA
    for <pritesh@xxx.xxx>; Mon, 15 Sep 2014 02:18:33 -0400 (EDT)
X-Spam-Threshold: 95
X-Spam-Score: 0
X-Spam-Flag: NO
X-Virus-Scanned: OK
X-MessageSniffer-Scan-Result: 0
X-MessageSniffer-Rules: 0-0-0-1427-c
X-CMAE-Scan-Result: 0
X-CNFS-Analysis: v=2.1 cv=ZunUdbLG c=1 sm=0 tr=0 a=Ig/UrxbkpOvRMQZiVkaGsg==:117 a=Ig/UrxbkpOvRMQZiVkaGsg==:17 a=mbVGFswbRTQA:10 a=HiVRdRxlSPgA:10 a=IkcTkHD0fZMA:10 a=RJWJd0NSAAAA:8 a=ZgKmBCKBAAAA:8 a=vGnWA2o9rr4c4ZYpt7QA:9 a=QEXdDO2ut3YA:10 a=RspQMrS_l_MA:10 a=0M4cGgZ80zEA:10
X-Orig-To: pritesh@xxx.xxx
X-Originating-Ip: [xx.xx.xx.xx]
Received: from [xx.xx.xx.xx] ([xx.xx.xx.xx:50602] helo=xxx.xxx)
    by smtp10.gate.ord1b.xxx.xxx (envelope-from <donotreply@xxx.xxx>)
    (ecelerity 2.2.3.49 r(42060/42061)) with ESMTP
    id 38/6F-11405-9B486145; Mon, 15 Sep 2014 02:18:33 -0400
Received: from AMAZONA-XXXXX ([10.8.1.100]) by xxx.xxx with Microsoft SMTPSVC(7.5.7601.17514);
     Mon, 15 Sep 2014 02:15:43 -0400
Date: Mon, 15 Sep 2014 02:15:43 -0400 (EDT)
From: donotreply@xxx.xxx
To: pritesh@xxx.xxx
Message-ID: <861597659.3125.1410761743468.JavaMail.AMAZONA-XXXX$@10.8.1.100>
Subject: check this mail
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
X-Mailer: ColdFusion 9 Application Server
X-OriginalArrivalTime: 15 Sep 2014 06:15:43.0469 (UTC) FILETIME=[7B10E1D0:01CFD0AC]

Answer 1

This header is OK, and is of no use for analysis. X-Spam-Threshold is set on receiving side, it is internal (configurable) score threshold to classify a message as spam (and you can not influence that); you should look at X-Spam-Score which is fine in this example.

For further investigation look at your server logs and find sessions where your mail was not delivered. Receiving side will usually give very clear reason for rejecting message.