Though not mentioned in the paper, Lincoln was famously aware of this technique.
> "Whenever Abraham Lincoln felt the urge to tell someone off, he would compose what he called a “hot letter.” He’d pile all of his anger into a note, “put it aside until his emotions cooled down,” Doris Kearns Goodwin once explained on NPR, “and then write [on the rear side of the sheet of paper]: ‘Never sent. Never signed.’ ” Which meant that Gen. George G. Meade, for one, would never hear from his commander in chief that Lincoln blamed him for letting Robert E. Lee escape after Gettysburg."
> "Whenever Abraham Lincoln felt the urge to tell someone off, he would compose what he called a “hot letter.” He’d pile all of his anger into a note, “put it aside until his emotions cooled down,” Doris Kearns Goodwin once explained on NPR, “and then write [on the rear side of the sheet of paper]: ‘Never sent. Never signed.’ ” Which meant that Gen. George G. Meade, for one, would never hear from his commander in chief that Lincoln blamed him for letting Robert E. Lee escape after Gettysburg."
From: https://www.nytimes.com/2014/03/23/opinion/sunday/the-lost-a...