Salutation in a breakup letter

DEARJOHN

This phrase starts many letters but takes a sad turn when followed by a name.

This clue plays on the phrase "Dear John," a well-known term for a letter where someone ends a relationship. The word "salutation" hints at the opening of a letter, like "Dear," while "breakup letter" points to the "John" part of the phrase. Together, they form "DEARJOHN," a direct reference to the classic breakup letter trope.