The line “Mirth is the Mail of Anguish” contains the essence of the poem. Thus, Dickinson tweaks the meter and employs internal rhyming of the “m” sound in order to make readers emphasize the terms “Mirth,” “Mail,” and “Anguish.” She also uses capitalization for this purpose. Through this line, the poet compares “mirth” to the chainmail worn by knights. Metaphorically, “Anguish” is the one (use of personification) who wears a mask of “Mirth” as chainmail for protection against criticism and humiliation.