Outlook header format

Microsoft Office Outlook 2003 ( 11.5608.5606 )

From: "Username" <username@sendinghost.com>
To: "'Username'" <username@receivinghost.com>
Subject: header test
Date: Sat, 28 Jul 2007 22:02:14 +0200
MIME-Version: 1.0
Content-Type: multipart/alternative;
    boundary="----=_NextPart_000_0003_01C7D162.F589D6C0"
X-Mailer: Microsoft Office Outlook, Build 11.0.5510
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1081
Thread-Index: DcfRUi9X1F1oqQo8TgRTgfuoq+BT/A==

Seems to be like Message-ID was with Thread-Index replaced.

Microsoft Outlook 2000 (9.0.0.2711) IMO ( Internet Mail Only ) Edition.

From: "Username" <username@sendinghost.com>
To: "Username" <username@receivinghost.com>
Subject: header test
Date: Sat, 28 Jul 2007 14:11:13 +0200
Message-ID: <NMBBKEGJPJBBOOBCOCGMKEACCAAA.username@sendinghost.com>
MIME-Version: 1.0
Content-Type: text/plain;
    charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
X-Priority: 3 (Normal)
X-MSMail-Priority: Normal
X-Mailer: Microsoft Outlook IMO, Build 9.0.2416 (9.0.2910.0)
Importance: Normal
X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2314.1300

Microsoft Oulook 97

Received: by localhost with Microsoft Mail
    id <01C7D126.F90D2860@localhost>; Sat, 28 Jul 2007 14:52:52 +0200
Message-ID: <01C7D126.F90D2860@localhost>
From: Username <username@sendinghost.com>
To: "'Username'" <username@receivinghost.com>
Subject: header test
Date: Sat, 28 Jul 2007 14:52:46 +0200
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit