You don't mention your version of RT, but you might be running into this:
http://issues.bestpractical.com/Ticket/Display.html?id=21411
Setting PreferRichText = 1 is a partial workaround.
On 12/11/12 5:48 AM, Marko Cupać wrote:
Requester has submitted ticket by e-mail from MS Outlook client. T
Requester has submitted ticket by e-mail from MS Outlook client. Ticket
has been created, but in web interface I do not see message body.
Automatic e-mail that informs tech support workers contains message
body of the original request, as inserted with $Transaction->Content()
in the template.
When