Hi,

are you sure that these properties are set by Outlook? I don't think so, at
least in some cases - i have send email(multipart/related , html) to my
exchange server and when I discover my Inbox using MFCMAPI tool I see that
PR_ATTACHMENT_HIDDEN property is set to true already(I suppose that MFCMAPI
app keep message intact and just shows its props).

In case i send the same mail to hMail server and view this mail using
outlook i see all attachments, i.e PR_ATTACHMENT_HIDDEN property is set to
false.

So my conclusion is that MS exchange server may mark some attachments as
hidden...

url:http://www.ureader.com/msg/10792293.aspx