Is it correct to write: “I am fine. I hope you are also well,” in formal letters?
Nope! We can't write: “I am fine. I hope you are also well.” in formal letters as formal letters are written to business matter or schools. But yep!, We can write “I am fine. I hope you are also well.” in informal lettes as in here, we write letters to our relatives, Friends, family. So, we can write anything or greet anything!