If I remember rightly Juno uses an web based email service, e.g. you view your email using your browser, is that correct?
If so then the email scanners won't scan it as this is http mail not POP3 email, unless you use some other third party software tool to convert it from http to pop3 email and download it into your email program.
If you view/download it using your browser then Standard Shield should scan the files as they are created in your browsers temporary internet files or saved on to your HDD.