Actually alanrf,
What you have said makes sense, as when I opened Outlook Express I noticed the email scanner service show in ZA, and when I checked the properties for the servers in Outlook Express I could see they had been modified by the Avast wizard.
POP3 127.0.0.1
SMTP 127.0.0.1
Then the account name with#pop3 in the middle
Also I did a test using Outlook Express, and the email scanner service showed up on ZA, so it does work, and there were 4 different ports on TCP it was listening to.