Is it illegal to open a letter sent to your address delivered through your letterbox but the name is someone you have never heard of even if you've lived there over twenty years? I have done just this, only to find the letter was from Revenue Protection Support Services demanding money off someone for travelling on the train without the right fare. They want ?18. I wrote to the company and said this person does not live here and now they've written back ignoring the letter saying they'll take this person to court. I checked websites and one says it is illegal to open a letter not addressed to you. But I did not know that when I opened the letters and anyway, I didn't ignore it - I did reply to the company. Also, I never believe what debt collection agencies tell me, such as private parking area companies. Anyway, anyone know the facts here?