Tim Cook answered
The Egyptian postal system is organized differently than in the UK or the US, and many Egyptians would not be as familiar with their postcode/zip code. The codes I have found for Heliopolis are 11341 and 11361, 11362 and 11363.
Egyptian Postcodes and What They Mean
Other Cairo postcodes include: 11566, 11827, 11762, 11851, 11742, 11521, 11728, 11628, 11553, 11519 and 11559. The figures indicate region/province/type of service/nearest post office (the last two figures) respectively. If you need to fill in an online form and don't know the postcode, and the system won't let you leave it blank, try any of the above. As long as the rest of the address is OK, your letter should get there.