Outlook suppresses "dangerous" attachments in received emails.
AFAIK, the help file on Outlook tells you how to set it to it's lowest limit, but last time I checked there was no way to get it to show the most "dangerous" filetypes - .exe, etc.
There is a patch you can get to enable Outlook to recieve .exe files etc. I have used it on my PC. I send round executable files a bit with workmates and its a pain in the arse to zip them everytime. I'll have a look and see if I can find it.