Can't add sky email account to Apple Mail

Up until yesterday I had a sky email account coming through to my Apple Mail on my iMac that worked just fine. Today it wouldn't connect when I turned my Mac on and kept asking for my password, which I knew was right but it kept coming up with 'unable to verify account name or password'. I tested my password on the Sky website and it is working fine. After several attempts and much frustration I decided to remove my sky email account and add it again - I chose the '@ Mail account' option, rather than Yahoo! on the right hand side list of accounts but still coming up with 'unable to verify account name or password'. I have also tried the Yahoo! option, which allows me to add the account but is then offline and nowhere can I see where to add a password or enable it!!! 😠

Any help would be much appreciated - very basic techy language please - preferably step by step guide for Mac users who really don't have a clue as to what they are doing! I am running macOS High Sierra.

Thanks!