Microsoft Installer octet-stream

I've started receiving files as attachments that are Excel 
spreadsheets, but labeled as "octet-stream" in the attachment header. 
When I run the file command on them, they are identified as
"Microsoft Installer". Why???

I've also received doc files identified the same 
way. Fortunately, there is a package that handles both types, and that 
is of course open office. So to handle it, I added the following in my 
exmh-defaults:

*magic_lMicrosoft Installer:      application/mscrap

Then in the mailcap, I added:

application/mscrap ; ooffice "%s"

Now all is hunky-dory.

Just thought i'd share.
-- 
rick baartman

TRIUMF
4004 Wesbrook Mall
Vancouver, BC
V6T2A3