Misspelled the index may result in your letter will reach the addressee not at once – first it to travel to the post office that you mistakenly indicated – and only then will be forwarded to the destination. Therefore, postal codes best to write without mistakes. But how do you know the code of the post office, to which "assigned" is your addressee?
First, you can read the index in any branch of Mail of Russia. Just name the city and the title (sometimes may require and the house number). Staff mail will be checked against a dictionary containing data for the service area of all post offices of Russia and will give you the desired index.
If you "make friends" with the search engines something in the mail to go is not necessary. On request "Russia index" or "index of N" and you will be able to find resources to learn the required. This information is not classified, and is available completely legally.
To find the database you are interested in the index, first select a town, then select a street. It happens that the house on the same street are served by different post offices. In this case, the website indicated on what basis they are divided. Select and write the index on the envelope, will not be mistaken!