BizTalk MIME Encoder - Filename issue

Question

Hi All,
I am using MIME enoder component. In order to assign a proper name for the attachment, I used the below code in a custom pipeline component.
attachmentPart.PartProperties.Write("FileName", "http://schemas.microsoft.com/BizTalk/2003/mime-properties","SampleXml - Copy.xml");
However, when I see the actual message that is transmitted (using fiddler), file name is encoded into some cryptic value like below..
Content-Type: application/octet-stream
Content-Transfer-Encoding: base64
Content-ID: {17DE6096-2E1A-4F6A-BD27-7F6532AE4E10}
Content-Description: SampleXml - Copy.xml
Content-Disposition: filename="=?utf-8?B?U2FtcGxlWG1sIC0gQ29weS54bWx=?="
My end system wants specific file name to be present in Content-Disposition. Does any one have any idea why this is happening and how to correct it ?
Thanks in advance...

Answer 1

For the benfit of others,
http://stackoverflow.com/questions/454833/system-net-mail-and-utf-8bxxxxx-headers has the answer for my question.
When I send a file with name: SampleXml.xml
and it is converted to “=?utf-8?B?U2FtcGxlWG1sLnhtbA==?=”
by MIME Encoder
Pipeline component.
Base64 encoded value of SampleXml.xml
is U2FtcGxlWG1sLnhtbA==