alias email addresses not visible to send from ..

Hi

I was having problems yesterday with email and i unticked an iCloud alias to delete but when i went into my email account after it all my email addresses except for the main one has disappeared. I am still receiving emails to those addresses and if i use my iPhone they are still there to send emails from but on my macbook pro there is no record of them to send an email from.

i am using a macbook pro 2015 with el capitan

any help would be much appreciated. I am assuming if the addresses are still working this is retrievable.

Thanks

Linda