05-02-2012 08:30 AM
It depends on the way the mail is stored locally, and I'm not sure how Postbox does it. In many cases, attachments do not actually get saved to disk when the mail is received, but only when the user explicitly saves the attachment (which is a built-in security measure in the mail client). In this case, the scanning by Norton Antivirus occurs at that point, when the attachment becomes a file in the local system, and thus a potential threat. There is no feedback about this unless/until a problem is detected (and trust me, you would be very annoyed if there was an indication each time a file was automatically scanned that had no issues).