It is only purchasable if you install their software, can't just buy such a stamp on the website if I'm reading the page correctly?

I seem to remember Deutsche Post also had a thing you could just write on the letter, or maybe it was DHL's parcel service instead. Those were purchased simply online like any other product/service and, after paying, it told you what to write in the corner. Or maybe I misremember and they only have this system where you can take the pdf to a parcel shop and have them print your label.

Edit: found the "print in store" option, it's not for letters but for parcels https://www.dhl.de/de/privatkunden/pakete-versenden/angebot-... "Don't have a printer? Let your stamp be printed at [places]."

It used to be also a squared code consisting of 12 digits, you could receive via SMS to 22122, but this method is deprecated or already even terminated. Has anybody tested it recently?

https://www.giga.de/tipp/briefmarke-per-sms-an-22122-erhalte...

Cool, I didn't know that. I still have a few self-printed QR code-type stamps. #PORTO is a nice option.

This is convenient. Do you know if sender tracking is available for these purchases? I tried getting one, but there was no sendungsnummer provided...

Denmark has had this for years. The code is 3 lines, each with 4 alfadigits. The code is valid for 180 days.

Same here in Norway.