Exchange 2010 help clearly states that SMTP message header removal or re-writing for content-type boundary is not possible through a transport rule and for good reason - message encryption etc..
So how do you get Exchange to exclude the server name and domain name at the end of the unique id in the first place.
This question has been asked in TechNet and no answer was provided. However, it does highlight that in some installations the server and domain is appended and in some installations it does not.
The issue is highlighted in the SMTP message header below. The reason for wanting to hide the server and domain information is that we provide email for three different domains and don't wish to link them.
Date: Wed, 9 Mar 2011 02:20:53 +0000
Accept-Language: en-GB, en-US
Content-Type: text/plain; charset="us-ascii"
Any help much appreciated.