Undeliverable Email message when someone sends me an email?

So people from different email accounts will try to send an email to my @me.com or @icloud.com accounts (they are the same email the two are joint) and the email gets trough to me, but they get an email right back that says the email is undeliverable which makes it confusing for people wondering if I got the email. for some reason my old @Hotmail.com email account pops up in there and it has never been used with my icloud email. I will post a picture it might be somewhat confusing.