Terry Zink, an MVP, wrote a good article about the difficulty most common e-mail filters have at stopping phishing impersonation attacks using simple display tricks.
It's possible for Synology devices running DSM 3 or higher to enable support for NTFS ACL's. This allows Windows-users to set up Security through Windows Explorer itself. Most of the ACL types are supported.
NTFS ACL's have to be enabled for a share through the web-interface: