Threatening letters

(Law) letters containing threats, especially those designed to extort money, or to obtain other property, by menaces; blackmailing letters.

See also: Threatening

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in classic literature ?
Seized with an indescribable fury, they addressed threatening letters to the different members of the Gun Club by name.
Five times in the last fortnight he's had threatening letters left at my flat, and I can't even find out who leaves them, let alone if it is Welkin himself.
"Yes," replied Smythe coolly; "they can't tell me who left those threatening letters at my flat."
Nobody writes threatening letters about money to this place.
Perhaps he connected it in his own mind with one or two outstanding accounts, in reference to which he had already received divers threatening letters. His countenance fell as he replied,
"On the very top of Sir Isaac's papers," explained Harker, "there was a threatening letter from a man named Hugo.
Two men and a woman, all employees of the Kenyan office of the UN High Commissioner for Refugees, are accused of asking a refugee to write threatening letters as though they were from Saudi exile Osama bin Laden.
The court heard that Dougan sent threatening letters to Mr Mason's partner in Telford, Shropshire, prior to the alleged attack.
She allegedly sent threatening letters to the Douglas family for a year.
Nursing director Stephen Milloy said: "Our patients should not be getting threatening letters from people who are there to care for them."
"Cyril Dennis has not received any threatening letters from us."
No-one has admitted responsibility for the attacks but seven members of the hunt received the threatening letters on September 4 - two days after hunt saboteur Steve Christmas was seriously injured while following a hunt, in Horsted Keynes, West Sussex.