Hyde Park and Letter-writing

Once again, one of the key plot-threads in a Jacobean play is complicated by the "manipulation" of a written letter: that of Fairfield to Carol about his supposed malcontentment and potential suicide. This, of course, drives them closer together near the end. He suggests that the letter was in fact forged. In an era 200 years before letter delivery was rationalized and beaureaucratized, what does this apprehension and doubt surrounding the delivered "mail" suggest about beliefs in the cycle of communication and interpretation?