It's possible the person meant:
* Letter writing: This is a broad term that encompasses the act of composing and sending letters.
* Letter format: This refers to the specific layout and style used when writing a letter (e.g., block format, indented format).
* Letter style: This describes the tone and language used in a letter, which can be formal, informal, friendly, or professional.
If you can provide more context about where you encountered the term "letterese," it might be possible to figure out what the person meant.