Historic Letters: Emily Dickinson
I invite you to browse the online Emily Dickinson Museum where you can get better acquainted with the poet. I'll temp you with the following quote and image of "Emily Mail." She is described as a "gifted epistolary artist." I think that description well worth aiming at by the rest of us.
EMILY DICKINSON, PRE-EMINENT POET, also distinguished herself as a writer of letters, which she regarded as a “joy of Earth” (L960). Cryptic and allusive in style, dazzling in verbal effects, and sensitively attuned to her recipients, Dickinson was a prolific and gifted epistolary artist.
It strikes me that "cryptic and allusive in style" is more easily achieved than is "epistolary artist."