Exchange 2000 blocks certain file types as incoming attachments (e.g., .exe, .bat, .scr, and others). The Help files indicate this can be changed, so that these file types provide a warning to the user. But these file types can still be passed through Exchange 2000. How do you change the security file level from level 1 to level 2?
It's actually the Outlook 2000 SR1a Security Update that provides the blocking mechanism, and not Exchange 2000. The attachments are blocked by hiding the pointer or reference to them in the recipient's Outlook client. They are still present in the user's mailbox and Exchange administrators can control which attachments can be seen and by whom.
Understanding this security update, and the impact it will have on your users, requires careful reading of the documentation regarding it. Start by reading the update announcement on the Microsoft web site. Then, have a look at the links referenced at the bottom of the page.
This was first published in February 2001