All contents of letters that are made of materials other than paper, e.g. SIM cards, CDs, USB sticks, plastic cards, identity cards, badges, etc., cannot be scanned.
Letters containing PIN codes, money, tickets, vouchers, cheques, etc. cannot be scanned either, nor can formats larger than A3 or smaller than A6.
If the contents of a letter cannot or are not allowed to be scanned, the letter will be forwarded to the recipient in physical form.