I found this spooky little tale over in the archives of The Chirurgeon's Apprentice, a great blog to read around this morbidly-oriented season all about medical history and the culture surrounding the treatment of human remains.
On 14 February 1829, the Morning Herald reported a story about a woman who had recently died and been buried in a village near Mansfield in Nottinghamshire. Before dying, she had asked a close friend that the letters of her dead son be placed in the coffin beside her body after she had died. The friend—distraught by the woman’s eventual death—forgot to do this and became very distressed after the funeral. Fortuitously, the village postman died a few days later and the woman arranged to have the letters put into his coffin, as ‘she firmly believed that he would be as diligent a postman in the other world as he had been in this’.
I'm sure he was! Happy Halloween!