Solved! Step Mother's Email Address Changed When I Replied

Aug 28, 2018
Received Email from parents-most definitely their long established email addy. However, when I replied, after having written long response, I noticed too late that in To: box, prior to Send, was a completely unfamiliar email addy- not remotely close to theirs. I asked my dad about it, all he knew was that he's not getting any email from his pals but doesn't know what the Spam or Junk files are. So, I Googled addy and it came up close to a U of Delaware campus addy. My parents are in the FL Keys. That's as far as I could go on Google and Wiki. No attachment but there was a clip near the Subject: which of course I'd never open.