delivery status notification failed from postmaster@hotmail is what I get everytime I tried adding email accounts

Can someone help me with this very simple task which I successfully did in the past but it is now pathetically a failure, frustrating and ridiculous. I followed all the instructions of going to mail then setting, tapping accounts and .... nothing works. So here's what I was and still is trying to do: I wanted to create 2 additional email accounts. From the mail app, it didn't work. I then went to outlook account and was able to set up the additional email account/aliases. I thought I did until I tested it and in my inbox I got "delivery status notification (failure)". I removed the added account aliases and repeated the process of adding email accounts. Same thing - "delivery status ..failure". I'm sure you know what to do. Thank you.