In The Trash. A friend reports several hundred unsolicited email messages each day. Well-written direct mail works.
Letters are a very personal form of communication.
Even when you know the same letter was sent to thousands of people, it still has some of the feel of a personal note from a friend. People who are good at writing sales letters know this and use it. They do their best to create a personal bond between the letter and the reader. Your sales letter should talk intimately with the reader. Chat informally with short sentences and simple words.