missive
1. [ noun ] (writing) a written message addressed to a person or organization
Synonyms: letter
Examples:

"wrote an indignant letter to the editor"

Related terms: text document invitation cover_letter open_letter form_letter epistle encyclical fan_letter chain_letter round_robin pastoral airmail_letter crank_letter business_letter dead_letter letter_of_intent personal_letter correspondence mail line PS address
Similar spelling:   misgive
  massive
  mischief