I’m not using Outlook, but: there is a junk-folder, that was created by avast inside Outlook? Then there must be some kind of setting in the avast gui to enable that function.
Alternatively you could create a rule in outlook that moves all mails that have the “*** SPAM **” in their subject.
Not using avast! Internet Security or Outlook Express either, however you can download the “avast! Internet Security 5.0 - Quick Start Guide” at: http://www.avast.com/download-documentation
Below is from Page 16 of the Quick Start Guide: " … Finally, on the Main Settings page you can specify exactly how suspected spam emails should be marked, e.g. SPAM. This can be used to create a rule in your email client, for example to automatically move marked emails to another folder."
Hence per the above, you’ll need to setup avast! how you want to mark suspected emails, then in Outlook Express create a rule that moves the marked emails to the folder of your choice.
From the OP’s post: “I have just purchased Avast 5 and have been looking forward to all those spam emails being thrown into the Avast junk folder in outlook express. …”