The handwritten notes on the stationery of the so-called Islamic Emirate of Afghanistan were traditionally sent to those alleged to have worked with Afghan security forces or US-led troops, listing their "crimes" and warning that a "military commission" would decide on their punishment.
They would close with the mafia-style caveat that insurgents "will take no further responsibility for what happens in the future."
But nowadays the Taliban say they have mostly ceased the practice, while those selling forged threat letters are doing a brisk business as tens of thousands of Afghans flee to Europe, hoping to claim asylum. Forgers say a convincing threat letter can go for up to USD 1,000.
"To this day I have only ever known one guy who genuinely got a threat letter from the Taliban. All the rest are fake," he said.
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There is no shortage of customers. With unemployment at 24 per cent and the insurgency raging across much of the country, the government expects that 160,000 Afghans will have left by the end of the year, four times the number of departures in 2013.
Last month, Germany's top security official complained of an "unacceptable" influx of Afghans from relatively safe areas of the country. Germany, a longtime contributor to international forces in Afghanistan, currently has more than 900 soldiers in the NATO-led training mission there.
Germany's Federal Office for Migration and Refugees said it was aware of the letters but that no statistics are kept on them. Spokeswoman Susanne Eikemeier said that since such letters are not official documents, the weight granted to them is generally limited.
Even the Taliban, who have stepped up their 14-year insurgency in recent months and spread to new areas, say most of the threatening letters are forgeries.