There are many reasons why someone need to send an anonymous letter. Bad relationships are probably  the bigest reason. This is a great way to comunicate with an ex-partner or friend without that person knowing where you live. In fact that person will look at the postmark and think for sure you must live in or nearby that postmark city. This can send then on a wild goose chase while you sit back and laugh. A person once wrote a letter saying how sorry they were giving the impression they wanted to make up. Well that person went looking for them in city far far away. In the mean time the letter writer was in the prosscess of moving in the other direction. Another good prank is to send a post card making someone think they are on vaction in a place where their friend allways wanted to go.  A great remail service can be found at http://quickremail.com