Can people who send E mails thru yahoo mail tell if you do or do not read them?

I have a now ex friend who is bugging me, they have concocted some sort of way I have hurt them, wierd, becuz I didn't. They sent a couple of inconsiderate E mails and I figured that they just wanted to vent everything bad, they say I am responsible for so I did not respond and the E mail seemed to me that they had the wrong person, wrong situations so I did not respond and figured that was the end.Yet they still send me info E mails, do they think I really want to hear from them after they trashed me? Am shocked still getting E mails. I don't want to block them in case it gets really haring, I want proof, as this person is an addict to drugs and I believe now has the ability to become dangerous. I want proof in case I have to file a restraining order. I hope it doesn't come to that. Can they tell I am not reading the E mails ? and maybe get the hint I am not interested in anything from them anymore? I am kind and have always been a good friend, wierd???!!!!!! Thanks for any help