I've sent you a PM Andy. I've just tried sending an email from a Plusnet account to a Force 9 one and it went through IronPort.
This one was from Webmail:
Return-path: <me@privacy.plus.com>
Envelope-to: me@privacy.force9.co.uk
Delivery-date: Fri, 28 Nov 2008 00:14:36 +0000
Received: from [212.159.7.33] (helo=mx.ptn-ipin01.plus.net)
by fhw-sunmxcore21.plus.net with esmtp (PlusNet MXCore v2.00) id 1L5r0G-0003rf-KL
for me@privacy.force9.co.uk; Fri, 28 Nov 2008 00:14:36 +0000
Authentication-Results: mx.ptn-ipin01.plus.net; dkim=neutral (message not signed) header.i=none
Received-SPF: None identity=pra; client-ip=212.159.0.97;
receiver=mx.ptn-ipin01.plus.net;
envelope-from="me@privacy.plus.com";
x-sender="me@privacy.plus.com";
x-conformance=sidf_compatible
Received-SPF: None identity=mailfrom; client-ip=212.159.0.97;
receiver=mx.ptn-ipin01.plus.net;
envelope-from="me@privacy.plus.com";
x-sender="me@privacy.plus.com";
x-conformance=sidf_compatible
Received-SPF: None identity=helo; client-ip=212.159.0.97;
receiver=mx.ptn-ipin01.plus.net;
envelope-from="me@privacy.plus.com";
x-sender="postmaster@pih-cgirelay03.plus.net";
x-conformance=sidf_compatible
X-SBRS: 5.3
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: Aq0AAFvGLknUnwBhmWdsb2JhbACSVIEVAQEBAQEICwoHEb0qgn0
X-IronPort-AV: E=McAfee;i="5300,2777,5447"; a="2893939"
X-IronPort-AV: E=Sophos;i="4.33,678,1220223600";
d="scan'208";a="2893939"
Received: from pih-cgirelay03.plus.net ([212.159.0.97])
by mx.ptn-ipin01.plus.net with ESMTP; 28 Nov 2008 00:14:36 +0000
Received: from [212.159.6.52] (helo=webmail.plus.net)
by pih-cgirelay03.plus.net with esmtp (Exim 4.63)
(envelope-from <me@privacy.plus.com>)
id 1L5r0F-0004g5-Lb
for me@privacy.force9.co.uk; Fri, 28 Nov 2008 00:14:35 +0000
Received: from 80.229.150.170
(SquirrelMail authenticated user bobpullen)
by webmail.plus.net with HTTP;
Fri, 28 Nov 2008 00:14:28 -0000 (UTC)
Message-ID: <16021.80.229.150.170.1227831268.squirrel@webmail.plus.net>
Date: Fri, 28 Nov 2008 00:14:28 -0000 (UTC)
From: me@privacy.plus.com
To: me@privacy.force9.co.uk
User-Agent: SquirrelMail
MIME-Version: 1.0
Content-Type: text/plain;charset=iso-8859-1
Content-Transfer-Encoding: 8bit
X-Priority: 3 (Normal)
Importance: Normal
X-pn-pstn: Spam 0
Subject: Sent from webmail
And this one was sent via the relays:
Return-path: <me@privacy.plus.com>
Envelope-to: me@privacy.force9.co.uk
Delivery-date: Fri, 28 Nov 2008 00:15:59 +0000
Received: from [212.159.7.33] (helo=mx.ptn-ipin01.plus.net)
by fhw-sunmxcore05.plus.net with esmtp (PlusNet MXCore v2.00) id 1L5r1b-0004kN-2Q
for me@privacy.force9.co.uk; Fri, 28 Nov 2008 00:15:59 +0000
Authentication-Results: mx.ptn-ipin01.plus.net; dkim=neutral (message not signed) header.i=none
Received-SPF: None identity=pra; client-ip=212.159.14.19;
receiver=mx.ptn-ipin01.plus.net;
envelope-from="me@privacy.plus.com";
x-sender="me@privacy.plus.com";
x-conformance=sidf_compatible
Received-SPF: None identity=mailfrom; client-ip=212.159.14.19;
receiver=mx.ptn-ipin01.plus.net;
envelope-from="me@privacy.plus.com";
x-sender="me@privacy.plus.com";
x-conformance=sidf_compatible
Received-SPF: None identity=helo; client-ip=212.159.14.19;
receiver=mx.ptn-ipin01.plus.net;
envelope-from="me@privacy.plus.com";
x-sender="postmaster@pih-relay06.plus.net";
x-conformance=sidf_compatible
X-SBRS: 4.7
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: AoUBAFvGLknUnw4Tk2dsb2JhbACMXQGFdoEVAQEBAQcLCgkRA70nB4J2
X-IronPort-AV: E=McAfee;i="5300,2777,5447"; a="2894283"
X-IronPort-AV: E=Sophos;i="4.33,678,1220223600";
d="scan'208";a="2894283"
Received: from pih-relay06.plus.net ([212.159.14.19])
by mx.ptn-ipin01.plus.net with ESMTP; 28 Nov 2008 00:15:50 +0000
Received: from [80.229.150.170] (helo=relays)
by pih-relay06.plus.net with esmtp (Exim) id 1L5r13-0005rb-TX
for me@privacy.force9.co.uk; Fri, 28 Nov 2008 00:15:50 +0000
Message-Id: <E1L5r13-0005rb-TX@pih-relay06.plus.net>
From: me@privacy.plus.com