Language is a wonderful thing. The internet is also a wonderful thing. But what does the word 'internet' really mean? The Cambridge dictionary gives this definition:
noun [ S ]
the large system of connected computers around the world that allows people to
share information and communicate with each other
But the Collaborative International Dictionary of English says this about it:
internet (ĭntẽrnĕt), n. A large network of numerous computers connected through a number of major nodes of high-speed computers having high-speed communications channels between the major nodes, and numerous minor nodes allowing electronic communication among millions of computers around the world; -- usually referred to as the internet. It is the basis for the World-Wide Web.
One word, two definitions. One is about the internet, the other an internet. The latter implies that there can be more than one internet. And this makes sense, because the essential components that make up the internet can be used to create another "network of networks" that is disconnected from the internet that served you this article.
...and there is our problem. If we have two separate internets, which one is the internet? Well, the people who were coordinating the transition from ARPANET, the precursor to the internet that was funded by the U.S. Department of Defense, to the internet we know today, recognized this problem. They maintained a clear distinction in RFC's 871 and 872. Definitely check out the latter for a nice Winnie-the-Pooh excerpt. Anyway, an 'internet' was a network of networks, and the 'Internet' was the large network that all those universities and military installations were connected to. This use of capitalization was not just common in the protocol pushing circles. The Associated Press and New York Times for example only formally switched to the lowercase style 'internet' in 2016, the latter stating that such a change is common practice when newly coined or unfamiliar terms become part of the lexicon (see It's Official: The 'Internet' Is Over, archive).
This again makes sense. Why bother with special capitalization when everyone is familiar with it and can agree on what it means? And so, in most of the English-speaking world, we now write 'internet' in lowercase. I've been living in Amsterdam all my life, and although most waiters and bartenders here somewhat lazily assume that I'm either an expat or a tourist, the newspapers here are written in Dutch, and the newspaper companies have their own style guides. The Volkskrant for example made the change from 'Internet' to 'internet' between 26 February 2000 (archive) and 4 March 2000 (archive). The NRC switched between 15 April 2000 (archive) and 26 September 2000 (archive). A whopping sixteen years ahead of the AP and New York Times!
And the Government of the Netherlands? There have been some inconsistencies in the past, take for example this official parliament document from the minister and state secretary of finance, published on 13 April 2000. The document uses 'internet' and 'Internet' interchangeably. And this is to be expected, because as our Government changes frequently (at least once every four years), it is likely impractical to maintain a style guide like the newspapers, which often have the same editors employed for a much longer time. Nowadays though, you likely won't find any use of the old 'Internet' style in Dutch government circles.
One special (and definitely more stable) member of our Government is the monarch. The royal family has an archive of official documents, and one recurring speech that can be found in the archive is the yearly Speech from the Throne. The very first one that mentions your favorite time sink is from 19 September 2000. Interestingly enough, the original Dutch version uses the lowercase 'internet', while the English translation writes it as 'Internet'.
One final thing I want to dwell on are announcements from governments like those of Russia, declaring their intent to create an autonomous 'Russian internet'. China's Great Firewall and geo-blockades that have been a part of the internet for a long time are more examples of cyber-balkanization. Even though we are connected to the same internet, yours may be very different from mine. If you look at it this way, spelling 'internet' with a capital I is just silly.
P.S.: in the Netherlands, we refer to electronic mail as 'e-mail', not 'email'. Email has a very different meaning here. You can reach the author of this website by both electronic mail and regular mail, although the latter is not so regular anymore.