letter writer

noun3

1. •
   A correspondent; a writer of letters.
2. •
   A person employed to write letters for illiterate people; a person who does this as an occupation.

   • The Indian letter-writers, awaiting clients, fresh paper and carbons rolled into their machines, greeted Victor Crabbe with smiles and waved hands. — 1956
3. •
   A book containing examples of letters that can be imitated by those who wish to write correspondence.