How does the United Nations process and route outgoing mail?

The United Nations has its own international postal service, the United Nations Postal Administration. To outward appearances, at least for the post-sending public, it functions like any other national postal service. They’ve got service counters (albeit only three, one each in New York, Geneva, and Vienna) that sell their own special stamps, which can be used to post letters from the UN to anywhere in the world. UN stamps are denominated in the local currency but are valid only for posting from the UN office. I think this arrangement is sufficiently unusual that later today I’ll be taking my entire batch of holiday greeting cards to the UN for posting. (A couple of the recipients collect, or used to collect, stamps, so I wonder if they will notice.)

Anyway, I was wondering how the UN mail service works on a deeper level. What happens after I put the stamps on my cards and drop them in the UN mailbox? How and where are they sorted and routed? Does the UNPA have its own local sorting office for external mail? Do they bundle all the letters themselves according to the destination country and then take them to the airport for onward routing to the respective postal administrations? Or does the UN just take all the letters and hand them over to the local postal administration (USPS, Swiss Post, or Österreichische Post) for processing?

UNPA is basically an inter-organization courier service, with stamp issuing authority.
See Resolution 454

Thanks, but it’s not clear to me how this answers my question. What happens to a letter when I post it at the UN?

Read the resoluition. It has the Agreement between the UN and the US in the Annex and that says the United States Postal Service will operate the said post office.

All I could find is that they exist solely to print pretty stamps for collectors and you are limited to buying no more than 100.

So the letters I dropped off just now at the Vienna International Centre are going to get sent to the United States Postal Service? If so, that’s pretty cool, but a terribly inefficient way to send mail. (Unless the USPS maintains a sorting office here in Vienna, in which case that seems like a terribly inefficient way to run a postal service.)

That limit must be per transaction. Nobody at the stamp counter took down my name and ID, so I don’t see how they can stop me from coming back the next day for more.

By the way, I can attest that they’ve got some pretty nice stamps there, and a fairly large assortment of them at that. The office was even selling stamps denominated in Swiss francs and US dollars, though it’s not clear that I would have been able to use those to send mail from Vienna. (I suppose I could have asked, but the euro stamps looked nice enough for me.)

No cite, but it will most likely be given to the local mail authority and processed according that authority’s procedures. In the absence of a common carrier for mail from a unique location local services manage the packages. Not law, just how it works.

I’m sure that’s how it works; the local postal services already have the infrastructure to route international mail, so why reinvent the wheel?

Routing international mail is the cheap part. Delivery is the expensive part. By international agreement, countries accept international mail for free, in exchange for sending international mail. This works out very well for countries like Hong Kong, which have low internal delivery costs and export a lot of packages, but poorly for countries like Australia, which accept a lot of international delivery, but have very little export mail to help pay for it.

So the UN could probably make a profit by joining the international mail agreement as a “country”, accepting international mail, transporting it internationally, and dumping on the destination countries for delivery.

But since the international transport isn’t the main cost, it also makes sense for the USPS to just accept that cost as international good will, and be thankful that UN members post disproportionally international mail.

Some of you are assuming that it is about sending mail; it isn’t. The whole purpose is to sell stamps to collectors, and post offices throughout the world seem to be prepared to deliver mail with those stamps on. I guess that the numbers are infinitesimal compared to domestic mail so it just gets swallowed.

I doubt that anyone in the USPS can identify the stamps used all over the world well enough to check their validity anyway. It’s always up to the sending country to ensure that the correct postage has been paid.

That is not true, at least not anymore. A treaty concluded in 1874 indeed provided for the principle that each country would accept incoming mail for free, which, by reciprocity, would mean that it gets to keep all the postages paid on outgoing mail routed to other countries. This system works if you assume that each mailed item triggers a reply in the reverse direction. But later it was realised that this was not the case, and many countries had massive imbalances between incoming and outgoing mail. So as early as 1969, the Universal Postal Union, the international organisation which oversees this system, introduced terminal dues, which are fees intended to compensate for these imbalances. There was a major hiccup this year between the United States and the rest of the system concerning the terminal dues applicable to parcel deliveries from China, which the US said were so low as to provide an unfair advantage to Chinese companies providing mail order delivery services to American customers. The dispute has meanwhile been resolved.

For a little information on this last, see: U.S. Avoids Postal 'Brexit' With Universal Postal Union Deal | Time

My father’s last job at the UN was to be in charge of an operation that sold UN stamps to collectors outside the US. There was a different department for sales within the US. He had a reasonably large staff, so it was pretty profitable.

The UN at least cancels stamps. I was born about the time UN stamps were, and he collected every one, even before he got a job in that department. He also collected first day covers, and once he managed to convince the operation to cancel a cover, with the same date, in both Geneva and New York.

I got the impression that the mail in the UN was handed off to the USPS, but I don’t know how much it got sorted. The volumes were not all that high, so I doubt it was a big issue. Sadly he isn’t around any more to ask.

I expect there will be a similar agreement with the Austrian Post, but UNPA’s own webpage in Austria happens to be broken. There might be other ways to search for it but I suspect they’d be more likely to be in German than in English.

After all, the only difference between mail posted at a UN site and that posted at any kind of company or organization with a bulk mail agreement is the stamp. At UNPA you can get a sticker, in the other ones it’s either preprinted on the envelope or stamped with an ink-stamp.

The Austrian government has this agreement (in German) on its website, which Austria has concluded with the United Nations in 1980. It permits the UN Postal Administration to issue stamps in Austrian currency (shilling at the time, euro now) and states that the post office on the UN premises in Vienna is run by the Austrian mail authorities. The revenue from stamps which this post office sells for items mailed through it are kept by the Austrian mail authorities, but the UN is allowed to sell stamps to philatelists directly and keep those revenues.

So economically, it means that if you use the UN post office for actual mailing, it operates, from a business point of view, as a normal Austrian post office. The real business case for the UN thus lies in selling stamps to collectors who never use the stamps for postage; revenue from the sale of those stamps is retained by the UN.