I seen the cds in stores there way too much thats all and I been scammed before thats all
Don't know what stores you have seen avast in as they aren't distributed in this way.
Yes it does scan emails, I suggest that you browse the avast User Interface (avastUI) to see what shields it has, it is very comprehensive.
I have been using the avast free versions for eight and a half years in all, just renew the registration each year.