Unable to verify email account on Mac or Macbook

My Mac and Macbook keep asking me to verify my hotmail account. Even though I am definitely entering the correct password (from keychain - that works when I log into the account on Safari) it keeps saying unable to verify account. This still persists if I remove the account and then add it again and whether I enter the password in Settings > Accounts or on the mail app. It seems like this issue has been going on a while. What is the fix please? I've tried all the other fixes but none of those work.