Good idea to check which of my three email addresses was the target. I am a shut-in, so I do a lot of online shopping. It might be tricky to figure out who the culprit was, but it's a good place to start.
I am terrible at rules! They are sort of like high school algebra to me, and I was lousy at that. I do plan to give it a go though.
Thanks again for your help, Brit Tim.