Does Avast home edition protect Outlook Express from spam???
In a nutshell No
avast is only an antivirus not an antispam.
What you need is a filter for your email which, as the others have stated, avast does not do since it is an antivirus and not an anti-spam program. You might want to try Spamihilator which works with Outlook Express. You can find a download for it at the link below but read about it and then make your own decision. It is free to use and be sure to click on the screenshots on the link.
http://filehippo.com/download_spamihilator/