When using EWS Managed API to send Email via Exchange Server 2007.
I noticed that MAPI clients like MS Outlook display all custom headers.
But when I use POP3/IMAP clients like MS Outlook Express.
I have noticed that these custom headers do not display in the message opened from MS Outlook Express.
Is there a setting in Exchange Server 2007 that we can set to make these custom headers propagate and be received by a POP/IMAP client? Also why do custom headers in example below display up in lower case in MAPI clients like MS Outlook? But surprisingly if we use SMTPClient class to send email then these headers display as sent with Case Sensitive letters. eg. Header.

Example of Headers received by a MAPI client like MS Outlook via Exchange Server 2007

Received: from EXMAILVS1.blabla.com ([]) by  
cashtp02.blabla.com ([XXX.XXX.XX.XXX]) with mapi; Mon, 20 Dec 2010 12:17:05  
Content-Type: application/ms-tnef; name="winmail.dat"  
Content-Transfer-Encoding: binary  
From: asfsdf <adasd_asdfdsf@adsad.com>  
To: asdsdf <aaa@aaa.com>  
Date: Mon, 20 Dec 2010 12:17:04 -0800  
Subject: Please send me this header  
Thread-Topic: Please send me this header  
Thread-Index: AQHLoILek7g5cFgHQU6lHHfiKkdUMg==  
Message-ID: <69804E0B6B987142A0F637D5495AB88451620AEA09@EXMAILVS1.assds.com>  
Accept-Language: en-US  
Content-Language: en-US  
X-MS-Exchange-Organization-SCL: -1   
X-MS-TNEF-Correlator: <69804E0B6B987142A0F637D5495AB88451620AEA09@EXMAILVS1.asdfsa.com>  
customheader1: hello ali  
customheader2: hello Jace  
MIME-Version: 1.0  
  • Sounds more suited to ServerFault.com I think, since it's likely an Exchange Administration issue. – Will Hughes Dec 20 '10 at 22:59

Custom/Modified Headers can be propogated by MS Exchange Server 2007 to Non-Mapi clients using POP/IMAP.
But we need to run the following command: Set-TransportConfig –HeaderPromotionModeSetting [MayCreate | NoCreate | MustCreate]
For E.g.: Set-TransportConfig –HeaderPromotionModeSetting MustCreate

In Exchange management shell use the above cmdlet to change the current behaviour. The default is NoCreate. You can choose either of the other modes.

MS Exchange Server 2007 only propogates custom headers in LOWER CASE.

  • While this will work as advertised, there are side-effects to this. Due to design limits Microsoft imposed on itself back in the MS-Mail days, there are only so many custom headers it can promote into the database as attributes. This limit is a hard limit. Since any X-ThingyMaBob: True header will be promoted, you can run out of space. It may take years, but it can be done. MayCreate should be used over MustCreate. – sysadmin1138 Jan 1 '11 at 1:12
  • @sysadmin1138 : These are design considerations of Microsoft. You have to use MustCreate over MayCreate and not as you say MayCreate over MustCreate. If you did as you say the headers will still not be created. I hope I am clear on this with you. RuruBoy is right in saying so. – user91209 Aug 10 '11 at 17:47

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