I want to put entire letter as a quotation in text (which is a book), something similar to what you get with
quotation enviroinment, but preserving positions of adress etc. How to do this?
One option would be to process the letter separately to a pdf and then use the pdfpages package to include the entire letter as a pdf. you can then scale the letter to fit whatever space you have. The package also works for multiple pages.