Death at Intervals

In an unnamed country on the first day of the new year, people stop dying. Amid the general public, there is great celebration: flags are hung out balconies and people dance in the streets. They have achieved the great goal of humanity - eternal life. Death is on strike. Soon though, the residents begin to suffer. For several months undertakers fake bankruptcy, the church is forced to reinvent its doctrine, and local 'maphia' smuggle those on the brink of death over the border where they can expire naturally.
Death does return eventually, but with a new corteous approach - delivering violet warning letters to her victims. But what can death do when a letter is unexpectedly returned?