Earlier quoted context omitted.
> It looks like it went through the automated letter sorter, too I understand the mail sorting depots can x-ray scan and read the contents of letters up to 4 pages of a4 folded, but that could have been hackers feeding me fake info in order to stop me writing letters. An example of the technique https://www.theguardian.com/books/2021/mar/02/researchers-re...
I'm not aware of any postal service that uses a method other then optical imaging for address reading. Further, in some countries such as the US, it is not legal for the postal service to "look inside" mail pieces without a warrant. While this type of 3D X-Ray technique is indeed possible it requires expensive specialized equipment and a great deal of effort, thus it being a major achievement for this university grou…
Most commercial mail carries an return address written on the reverse to avoid the need for this, and of course letters you write by hand should also provide a return address in principle although you're much less likely to send stuff to the wrong address than a commercial operation - when I heard my cousin had moved just before Xmas I didn't send her a card, because there's no point sending it to the wrong place and hoping it gets forwarded eventually, it's just an Xmas card.