Postcrossing Blog

Stories about the Postcrossing community and the postal world

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I don’t know about you, but as a member of Postcrossing, I take having an address for granted. I hadn’t thought about life any other way, nor put a lot of thought into my various addresses over the years. In the end, what got me wondering about it was helping out at Postcrossing, checking people’s addresses to make sure they were correct and learning about how different countries format their addresses.

Cover of The Address Book

Just at the right moment to answer some of these questions, I came across Deirdre Mask’s The Address Book: What Street Addresses Reveal About Identity, Race, Wealth, and Power. Do any of her opening questions — the ones that led her into the subject to begin with — sound as familiar to you as they do to me?

I set out to write a letter. I was living in the west of Ireland, and I had sent a birthday card to my father in North Carolina. I pressed a stamp on the envelope, and just four days later the card appeared in my parents’ mailbox. I thought, not particularly originally, that this should have been much more expensive than it was. And how did Ireland and the United States share the proceeds? Is there some accountant in a windowless back room of the post office, dividing each penny between the two countries?

In case you’re wondering, Mask does include the answers to those questions!

It was pretty surprising to me how much there was to say about addresses, and how little I’d thought about it. Mask picks apart the advantages and disadvantages of having an address, and discusses how some people in areas without addresses actually oppose any change. For people in politically unstable areas, having an address can be a bad thing, because it makes you easier to find — and no one is likely to be sending you postcards!

On the other hand, it makes all kinds of things more difficult: most documents for proving your identity rely upon you having an address and a traceable history. You can end up barred from working, having a bank account and signing up for government services, and once you’ve got into that situation, it’s difficult to get out.

It’s also surprising to me how recent some of these conventions are. Zip codes in the US were only introduced in 1963, and reading in Mask’s book about their introduction prompted me to look up the system of postal codes in the UK, introduced between 1959 and 1974. They’re so ubiquitous now that I didn’t even realise my parents might not have had postal codes when growing up!

Mr Zip advert
This is an image from a March, 1965 issue of Time magazine in which Mr Zip appeared, advertising the introduction of zip codes (Time, March 19, 1965, 92, via the Smithsonian).

One issue that Mask discusses that was particularly relevant for me (since I’m studying for my MSc in Infectious Diseases) was the importance of clear maps and precise locations for epidemiology. Ever since John Snow (not that one, GoT fans!) made a map of London to track cholera infections, epidemiologists have used maps and addresses to try to identify the causes of infection and the sites of transmission. Sometimes they need to use addresses to contact people and do follow-up work… but often the people most at risk of diseases like tuberculosis are people who have no fixed address, or live in improvised homes and shantytowns. How do we find those people and help them access the long-term treatment they need, without addresses?

The book is packed with all kinds of dilemmas like that — many of which I really hadn’t thought about before picking it up. It was pretty eye-opening, and I won’t be taking my address for granted again! What do you think; will you be giving this book a try? Has anyone already read it? I’d love to hear what you thought of it, if so!

The next review should be about Wish You Were Here (by Rita Mae Brown and her cat), but after that, I’m not sure! The Guernsey Literary and Potato Peel Pie Society features high on the list, since several Postcrossing members have asked my thoughts on it. I haven’t read it yet, but it’s ready on my shelf! But is there something you’d like me to review? You can make book suggestions to me in the forum thread I set up (you’ll need to be logged in to access it).

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Good news, everyone! After many requests, we finally opened a proper PO box for Postcrossing. So, if you’d like to send us a meeting card, show us some cool mail-related item that you found, or just say hi using a postcard, feel free to do so!

Here is the address:

P.O. Box 216
EC Tavira
8800–999 Tavira

We look forward to hearing from you! :)

P.S. – Depending on the volume of mail we receive, we might not be able to acknowledge all of it. So if you require an answer from us, the Contact form is a better way to receive a reply.


As promised, the first post on our behind-the-scenes series is about address validation. This is the process through which we check that all addresses in Postcrossing are (to the best of our knowledge) correct and complete.

The Little Mail Carriers helping us moderate addresses

“Red alert! Red alert! I think that one over there is missing the postal code!”

Addresses are one of the most important things in Postcrossing. Wrong or incomplete addresses would result in postcards being delayed or not delivered, and general unhappiness – which we would like to avoid.

There is specialized software to process addresses of course, but it’s either dodgy, specific to a country or just crazy expensive for our size. So, we chose to do this task ourselves, splitting the job between Paulo, Vicki and I. Each one of us picked a set of countries according to our strengths and learnt the UPU address format of those countries by heart. Most countries have their own format – and some are much simpler than others. We use this knowledge to go over thousands of addresses per week, spotting invalid ones, or just rearranging the order of the elements on the address. Most of the time, addresses will be read by automated sorting machines, which expect them to be written in a certain way. So if every address is formatted as UPU recommends, everything will go faster!

What makes an address invalid? Lots of things:

  • Parts might be missing: name, postal code, country name, etc.
  • The address might be written exclusively in the local script (Chinese, Thai, Cyrillic), making it hard to write for people who don’t understand that alphabet or those without a printer.
  • The address might be completely translated into English – which is usually a bad idea. For non-Latin scripts, transliteration works better and faster in our experience.
  • The address might not match the account’s location/country.
Technology helps with the last item on that list, because we can usually match your IP address to the location you’re signing up from. For instance, if a member with an IP address in Canada is opening an account in Fiji … something might be wrong, and we have to look into that. :)

A few postal operators also provide a list of all valid postal codes for their country, giving us the ability to automatically detect typos or invalid postal codes.

The Little Mail Carriers helping us moderate addresses

“Let’s just add the country name here at the bottom… I think it’ll help!”

The whole process of validating addresses has been streamlined over the years, but it still takes quite a bit of time, since every single new address needs to be checked and validated. We’ve been doing it for so long that by now we can tell at a glance whether an address is valid, incomplete or just in a strange order. We might not find all the problems – but we do spot lots of them!

Plus, we’ve learnt many nice things in the process too! For instance, did you know that an address in China should be written from the biggest component (province) to the smallest one (adressee) if written in Chinese characters, but the other way around if written in Latin characters? Or that there are no street names in Japan? Or that every house and building has its unique postal code in Singapore? It’s amazing!

I think that’s it for addresses, so I’ll leave you with one last tip: make sure that you write the address on your postcard exactly as it is shown – it’s already optimized for that country!

I hope you liked this first post on our behind-the-scenes series – we’ll get cracking on the next one! :)

Ana + Paulo @

“So… what do you do for a living?”

We get this question a lot, Paulo and I, especially at Postcrossing meetups. When we explain that we both run Postcrossing full-time, people often seem surprised to find out that the website doesn’t work automatically by itself. :)

Of course, static pages can almost run on auto-pilot, but Postcrossing is not static and it is constantly growing. Every minute that goes by, the website is being used and changed simultaneously by thousands of you, with hundreds of new members joining every day! At this scale, even some of the simplest tasks can be greatly amplified. Take for example, answering emails, finding postcard IDs, validating all the addresses or moderating the forum – these are some tasks which gradually became time-consuming for our small team.

But there are other, less visible things that we do, that are no less important. For instance: servers are maintained to keep the website running snappy and safe, code is developed, updated or fixed and we regularly improve our address selection algorithm so everyone can have a better experience. On the less technical side of our days, we keep in touch with postal operators, answer media queries and create content for this blog, among other things. So, overall, there are many small (and some not so small) tasks that keep us busy running the site.

Since so many people are surprised when we mention our job descriptions, we thought it might be interesting to show you what it’s like to run Postcrossing – and what it looks like “behind the scenes”. The first post on the series will be about address validation, and it will be posted in a few days.

Meanwhile, we’re collecting ideas for future posts, so this is your chance to chime in! Is there any part of what we do at Postcrossing that you’d like to know more about?