Personalized mail is simply a mail document that you have already imprinted with the recipients name and address. In other words, you have pre-printed your letter that is designed to be specifically delivered to the one person you have indicated on your document. This means we have to match the envelope to the letter. With a windowed envelope, this is easy, with a non-window envelope, this is time consuming. We charge an insertion fee for non window envelopes and personalized letter matching service.