Sent to who? You suggested the Yahoo email users contact
Yahoo. That won't every accomplish anything except a canned
reply. I think the mail server admin has more of a chance getting
issues investigated. And I'm not just blowing smoke out of my butt
I know this from experience as the former administrator of several small
and medium sized email servers. Anyways it's stopped for now. I've seen
a lot of oddities from Yahoo mail in my 15 years of using the service but
can't recall seeing duplicates.