Strange, I use the same feature when I’m on my notebook and nothing happens, i.e., avast let the messages on the server because like shgoh said, this is a mail client option.
Hmm, the use of Internet Mail provider is the only way to protect pop3/smtp mail clients. Outlook/Exchange do not use these servers and have to use a special provider with their own name. The change of settings is the only way to scan Internet Mail and other antivirus applications do the same of avast!
It’s strange the behavior… Does avast! delete from server even the clean (virus free) messages? :