Every year 250000 cards are destroyed by the postal authorities due to wrong or incomplete addresses. They say that a little more attention is paid to tracing the recipient of other consignments such as letters and parcels.
Sad but true that your Xmas card might not arrive to the recipient if you do not have the right the postal code. And on top of that, if you have a common name, and the street address exist in many towns then you might not get all the cards sent to you. But, if you do have an unusual name, as a friend of mine, who received a Xmas card from abroad with just his Surname and the country. The card was delivered just in time before Xmas too, even though it must’ve been sent very late. That must be a Xmas miracle!