[Mimedefang] Blocking CLSID attachments?

[Peter Campion-Bye]

Hi,
I just ran the tests at http://www.gfi.com/emailsecuritytest/ on my
MIMEDefanged server, mostly with success, however my setup (using FileScan
and clamd) failed to block the CLSID attachments, which have filenames
that look like this...
viewthis.{3050f4d8-98b5-11cf-bb82-00aa00bdce0b}
Anyone got any idea how to successfully block these in my filter?
Thanks, Peter