Mail from Exchange 2010 mailbox - BCC to Hotmail addresses with blank To: field not hounoured

Question

Hi
This feels related to a previous question
http://social.technet.microsoft.com/Forums/exchange/en-US/bec88844-79c1-4d17-bf73-9425842b22de/problem-sending-mail-with-bcc-and-without-to?forum=exchangesvrgenerallegacy but is slightly different - it just applies to Hotmail and related addresses (e.g.
hotmail.com, hotmail.co.uk, outlook.com, live.co.uk).
Sending from our Exchange 2010 to BCC addresses with blank To: field, the BCC is not being honoured, but just by Hotmail-related addresses. Any Hotmail-related recipient sent to in this fashion sees all their and other Hotmail-related addresses in the To:
field. But any other addresses to other mail hosts (gmail, yahoo etc) in the same BCC list aren't shown, and recipients at the other mail hosts have a fully hidden BCC list (i.e. see no To addresses at all).
If the To: field has an address then there is no problem - all BCC addresses are hidden for all recipients as expected.
It feels like it is the way the header is being handled by the Hotmail MTAs. But I only see this behaviour from our Exchange 2010 servers (including test servers).
Below are message headers from examples - anyone any ideas on this?
Thanks,
Gordon
Headers from the same message sent as a BCC to a "@live.co.uk" address and "@gmail.com" address with no To: field, and below that a header of similar with a To: field.
First message, sent from [email protected] (gets translated to
[email protected]) BCCd to
[email protected] and [email protected] with no To: address.
Seen in mailbox of [email protected] (note the "to:" field at the bottom - this is what is being shown in the UI):
x-store-info:J++/JTCzmObr++wNraA4Pa4f5Xd6uensaUSop/gUCq9urBwwSF/6FOwwl1Py7H+wW1z5lc55JnUJDXNvxmGUxkw/bnnWJePWYXWzuS5Ywv2HQzl2GD+3A6SoaKpjD5JlShFHg3JE6so=
Authentication-Results: hotmail.com; spf=pass (sender IP is 143.52.X.XX)
[email protected]; dkim=none header.d=shu.ac.uk; x-hmca=pass
[email protected]
X-SID-PRA: [email protected]
X-AUTH-Result: PASS
X-SID-Result: PASS
X-Message-Status: n:n
X-Message-Delivery: Vj0xLjE7dXM9MDtsPTE7YT0xO0Q9MTtHRD0xO1NDTD0w
X-Message-Info: NhFq/7gR1vQRHV6jbdvQfibhgw1iwvrSqdhXuaSscqGalY1BHnH2KCdI+PRBKCQiYnAlF/zI6HIxnd9XTtPz9XHPDwg5mATFcpFtv9WV5ImszG0/OtQaSIg5iX4MbuVLCVo+t2VN/SyhCbwRod9LNPet1UXZtp+Oho5aLYTKlYQVRQ8OWRHqxMCUhgER4oHof+Be4v85/e3u59xr9Q2GEVPOpY/FDKse
Received: from MTA2.shu.ac.uk ([143.52.X.XX]) by SNT004-MC4F19.hotmail.com with Microsoft SMTPSVC(7.5.7601.22712);
Wed, 10 Sep 2014 03:56:32 -0700
Received: from MTA1 ([10.14.XXX.XXX])
by MTA2.shu.ac.uk with esmtp (Exim 4.76)
(envelope-from <[email protected]>)
id 1XRfZg-0004Kn-9C
for [email protected]; Wed, 10 Sep 2014 11:56:32 +0100
Received: from CAS1.shu.ac.uk ([10.14.XX.XX])
by MTA1 with esmtp (Exim 4.80.1)
(envelope-from <[email protected]>)
id 1XRfZg-0002cz-2q; Wed, 10 Sep 2014 11:56:32 +0100
Received: from MBX1.shu.ac.uk ([xxxx::xxxx:xxxx:xxxx:xxxx]) by
CAS1.shu.ac.uk ([xxxx::xxxx:10.14.XX.XX%12]) with mapi id
14.03.0174.001; Wed, 10 Sep 2014 11:56:29 +0100
From: "user1" <[email protected]>
Subject: RE: PLease ignore yet again! testing Bcc again - no "to" field
Thread-Topic: PLease ignore yet again! testing Bcc again - no "to" field
Thread-Index: Ac/M5d+WfHZZ5GLGRsCfXxvcxsjnbw==
Date: Wed, 10 Sep 2014 10:56:28 +0000
Message-ID: <[email protected]>
Accept-Language: en-GB, en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-originating-ip: [10.14.XXX.XXX]
Content-Type: multipart/alternative;
boundary="_000_24BACA8040C3054487601DFC4087062C8C013974mbx1sh_"
MIME-Version: 1.0
to: [email protected]
Return-Path: [email protected]
X-OriginalArrivalTime: 10 Sep 2014 10:56:33.0151 (UTC) FILETIME=[E23190F0:01CFCCE5]
Seen in mailbox of [email protected]:
Delivered-To: [email protected]
Received: by 10.25.156.200 with SMTP id f191csp386624lfe;
        Wed, 10 Sep 2014 03:56:32 -0700 (PDT)
X-Received: by 10.194.200.137 with SMTP id js9mr48633666wjc.90.1410346592418;
        Wed, 10 Sep 2014 03:56:32 -0700 (PDT)
Return-Path: <[email protected]>
Received: from MTA1 (MTA1. [143.52.X.XXX])
        by mx.google.com with ESMTPS id cg3si20369633wjc.56.2014.09.10.03.56.32
        for <[email protected]>
        (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128);
        Wed, 10 Sep 2014 03:56:32 -0700 (PDT)
Received-SPF: pass (google.com: domain of [email protected] designates 143.52.X.XXX as permitted sender) client-ip=143.52.X.XXX;
Authentication-Results: mx.google.com;
       spf=pass (google.com: domain of
[email protected] designates 143.52.X.XXX as permitted sender)
[email protected]
Received: from CAS1.shu.ac.uk ([10.14.XX.XX])
by MTA1 with esmtp (Exim 4.80.1)
(envelope-from <[email protected]>)
id 1XRfZg-0002cz-2q; Wed, 10 Sep 2014 11:56:32 +0100
Received: from MBX1.shu.ac.uk ([xxxx::xxxx:xxxx:xxxx:xxxx]) by
CAS1.shu.ac.uk ([xxxx::xxxx:10.14.XX.XX%12]) with mapi id
14.03.0174.001; Wed, 10 Sep 2014 11:56:29 +0100
From: "user1" <[email protected]>
Subject: RE: PLease ignore yet again! testing Bcc again - no "to" field
Thread-Topic: PLease ignore yet again! testing Bcc again - no "to" field
Thread-Index: Ac/M5d+WfHZZ5GLGRsCfXxvcxsjnbw==
Date: Wed, 10 Sep 2014 10:56:28 +0000
Message-ID: <[email protected]>
Accept-Language: en-GB, en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-originating-ip: [10.14.XXX.XXX]
Content-Type: multipart/alternative;
boundary="_000_24BACA8040C3054487601DFC4087062C8C013974mbx1sh_"
MIME-Version: 1.0
Similar message sent with [email protected] in To: field:  from
[email protected]/[email protected] BCCd to
[email protected] and
[email protected] as seen in mailbox of [email protected]
x-store-info:J++/JTCzmObr++wNraA4Pa4f5Xd6uensaUSop/gUCq9v81cBAiz99O+8SxkfBVJ9NjbAXH8xe1rjvemR/ciBJT5MdkHvi8JYPj0vgDySrSfVnSG2OjgyyKNgjV2QF5PyGqXgRRVkQVM=
Authentication-Results: hotmail.com; spf=pass (sender IP is 143.52.X.XX)
[email protected]; dkim=none header.d=shu.ac.uk; x-hmca=pass
[email protected]
X-SID-PRA: [email protected]
X-AUTH-Result: PASS
X-SID-Result: PASS
X-Message-Status: n:n
X-Message-Delivery: Vj0xLjE7dXM9MDtsPTE7YT0xO0Q9MTtHRD0xO1NDTD0w
X-Message-Info: NhFq/7gR1vTvTqmPqDcS3ZKVZ4zJXdbe/WQhPCDn6U7TYJxfLAm+gALYf9z8EvjEIPauVTBwIF/uNFwreEfp3wgBZYYA8nUP8PFhNAMvRkDwCAnqdyWkFMZlNIQlCYkX84PJFTI7+qoRwxyIjAr2dfuXuj/qYYgN8IbRFD0FftK7d85hSKx/muFfL/1x713Efp1R2ztH/sUzvcxbXl+i8zHWvMqqF945
Received: from MTA2.shu.ac.uk ([143.52.X.XX]) by BAY004-MC6F14.hotmail.com with Microsoft SMTPSVC(7.5.7601.22712);
Wed, 10 Sep 2014 05:22:06 -0700
Received: from MTA1 ([10.14.XXX.XXX])
by MTA2.shu.ac.uk with esmtp (Exim 4.76)
(envelope-from <[email protected]>)
id 1XRguU-0006jA-4s
for [email protected]; Wed, 10 Sep 2014 13:22:06 +0100
Received: from CAS2.shu.ac.uk ([10.14.XX.XX])
by MTA1.shu.ac.uk with esmtp (Exim 4.80.1)
(envelope-from <[email protected]>)
id 1XRguU-0001YY-0a; Wed, 10 Sep 2014 13:22:06 +0100
Received: from MBX1.shu.ac.uk ([xxxx::xxxx:xxxx:xxxx:xxxx]) by
CAS2.shu.ac.uk ([xxxx::xxxx:10.14.XX.XX%15]) with mapi id
14.03.0174.001; Wed, 10 Sep 2014 13:22:00 +0100
From: "user1" <[email protected]>
Subject: test BCC - using own name in To
Thread-Topic: test BCC - using own name in To
Thread-Index: Ac/M8dJDWdvoIxoORH2RMAqNKM2m1w==
Date: Wed, 10 Sep 2014 12:22:00 +0000
Message-ID: <[email protected]>
Accept-Language: en-GB, en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-originating-ip: [10.14.XXX.XXX]
Content-Type: multipart/alternative;
boundary="_000_24BACA8040C3054487601DFC4087062C8C013A65mbx1sh_"
MIME-Version: 1.0
To: [email protected]
Return-Path: [email protected]
X-OriginalArrivalTime: 10 Sep 2014 12:22:07.0005 (UTC) FILETIME=[D63584D0:01CFCCF1]

Answer 1

I'm guessing that they're using something other than Exchange for the MTA's. I don't recall seeing this in the "Received:" headers ever since Exchange stopped using the MS Windows SMTP service:
Microsoft SMTPSVC(7.5.7601.22712)
--- Rich Matheisen MCSE&I, Exchange MVP