Most viruses in the wild today exploit security holes in Microsoft products and most of these viruses come through email. Microsoft has added a new “feature” which basically blocks all attachments so that you can’t get viruses unless you enable attachments. That way, Microsoft has deniability for their security holes. You wouldn’t get the virus if you didn’t enable the product to get attachments. It is a real cop out, because they should design the software right in the first place. Anyway, we virus scan your email before you get it, so you are pretty safe to begin with.
For instructions to change Outlook Express so that it will allow you to receive attachments, follow the instructions below.

1) In Outlook Express, go to the Tools menu at the top.
2) Click on Options

3) A new Window will appear. Click on the Security Tab (screenshot)
4) On the security screen there is check mark by a line that says “Do not allow attachments to be….” This line is about 1/3 of the way down. Remove the check mark.
5) Click OK