Securing Attachments

I've not been able to find anything relating to this:

emails received with attachments, if set to public://attachments will have a public url (this could entail legal issues if someone sends an attached file/document they expect will be kept confidential)

If attachments set to private://attachments, clicking on the attachment causes a redirect error (even when attempting to merely download the image, file etc).

Error message: The page isn't redirecting properly

Firefox has detected that the server is redirecting the request for this address in a way that will never complete.

This problem can sometimes be caused by disabling or refusing to accept cookies.