I've had four or five interesting experiences with "List" emails, they may be the ones you mention. I NEVER download something from an address that I don't PERSONALLY recognize. Or a forwarded attachment that was "endorsed" by a friend. So when I get an "unknown", I politely reply and ask that they "identify themselves so I can enjoy their attachment". Every time, I've gotten a message that the sender is UNKNOWN. Am I suspicious, cautious, etc? You bet!!! Carol in San Diego