It's not really possible in any easy way, and the possible ways are not
silent (ie the users will have to take some kind of action for it to work).
On Fri, Jan 27, 2012 at 12:13 AM, Chris Medical Device Co
Thanks try67. Consider this: I'm not trying to silently trick the receiver, either. I intend to explain to them up front that when they open the attached PDF, it will provide a signal that is the proof they have been notified. It's also okay if this isn't easy; I have IT people that can do it.