Since installing win 10, when sending emails, many come back saying undeliverable. Why? They worked fine in win 7

I am using google, yahoo and aol. Same problem with all of them. All 3 of my computers have the same results. Message says something about not being on the domino list. This puts me in limited contact, I actually have to use the telephone! It seems like I am limited to who I can contact by email. I can contact some people but not all. I have talked to some people and they have the same problem. All updates are installed. Dell computers, 64. Anybody have this problem? I am not using outlook

[Original title: win 10 email problems]