Can’t log back into Mail app after getting logged out for some reason?

I went to check my emails and all that came up was the options to sign into gmail, yahoo, iCloud, outlook etc. I’m with outlook but when I try to sign in it says it can’t as the account already exists. I tried to set up iCloud mail and that won’t work either.

I don’t understand why this happened as I checked my emails the night before and then the next morning it was like this.

Any help is greatly appreciated! :)