The whole idea of blocking various classes of e-mail can be somewhat tricky and controversial. I know of organizations that block all documents containing scripts, while others block all compressed files because they might be encrypted. This really comes down to a business decision. If you have a business need for these files, you probably don't want to block them completely. It's reasonable to rely on your mail server's antivirus software to detect and remove malicious scripts. On the other hand, if you're able to clearly identify those senders (say everyone at foo.com) that need to exchange script-laden files, you might want to configure your server to reject these attachments from anyone else.
This was first published in April 2006