On another, lesser, board I am in a dispute over the Gaza convoy thing. I posted a chart from The Economist listing the stuff Israel does not allow to come into Gaza. The list is unofficial, from a list the Palestinians developed.
http://i13.photobucket.com/albums/a275/PaulinSaudi/Graphics/GazaBlockade.jpg[\url]
So being devious, I went to the US Post Office site to cite the US Postal Manual, a favorite to read at bedtime. I hoped to find a list of items one may not mail to Gaza. I found nothing.
What items can we say with certainty are treated as contraband by the Israelis?
and also
What items are prohibited to be mailed to Gaza?
Maybe the Israeli post office wold be a better look?
Is Gaza treated as part of Israel, postally? I believe it’s separate telephonically, at least in theory.
Apparently, the Postal Administration of Israel is responsible for transferring mail to Gaza - once it’s there, I assume local authorities would take it. Thing is, the Israelis aren’t letting any mail in right now. Cite: http://www.usps.com/international/serviceupdates.htm#H27
So, to answer the OP: All items are prohibited to be mailed to Gaza, at least for now.
You can mail whatever you want to Gaza. Whether it gets there is another story.
Also, many countries agree with the US that Hamas is a “terrorist organization” so material aid to them in any form that is not carefully directed to “legitimate” charities may be considered aiding terrorism. You’re labelled a terrorist, please stay off our airplanes.
This is how Cat Stevens got on the no-fly list…
Wow, an area with no mail service? I have never heard of such a thing. Imagine that! Thank you all.
No chicken hatcheries or chickens, but they allow cartons for transporting the non-existent chicks?? 
So does Israel simply send everything back to the original sender, or is there a big warehouse outside Tel Aviv somewhere where all the mail that’s been sent to Gaza over the past several years is stored away? If the blockade ends, will the residents of Gaza be treated to several years worth of old junk mail, National Geographic Magazines and birthday cards from relative abroad being delivered all at once?