I did use correctly avast! before, but I changed my modem configuration (ADSL modem), and now avast! don't scan my emails...??
Strange but let's think a little:
1. Does your email client are configurated to use your new connection?
2. Does avast! is set to use DSL and not dial-up for update (Update (Advanced) page of settings)?
3. Have you check for scan Inbound and Outbound email into the Internet Mail provider settings?
4. Can you post your email accounts configurations? (pop3, smtp, username, smtp authentication...). If you want you can use other examples for that information then the real ones.