In 2013 PostNL introduced the “Postzegelcode” (Stamp Code). Simply put: by writing a number combination on the envelope after buying this code through the PostNL app, the letter could be put in the mail without stamps because the postage was correctly paid for. Initially, PostNL asked an extra 21 cents(!) for this service.
That of course did not work and the recent state of affairs was that people receive a discount when using a stamp code. PostNL was actively advertising this and the discount stood at 4 cents.
There were not that many reasons to use a stamp code to begin with. The argument that in this way valid postage can be purchased around the clock is true, but it is not really that special when you think about it. Letterboxes are only emptied at approx. 5 p.m. or 6 p.m. Also, nowadays stamps are available at supermarkets in even the smallest villages and as a rule their opening times are between 8 a.m. and 8 p.m. or even longer.
We philatelists, of course, abhor this type of postage: it is the harbinger of the disappearance of the stamp. However, as of January 1, 2020, PostNL has realigned the price of the stamp code mail with that of stamped mail: 91 cents. Good news for the stamp collector!