As pritambaral mentioned, they can make some minor changes to the server that are just enough to cause the client to no longer work.

This isn't exactly unheard of when it comes to Microsoft. I mean, you don't have to go far to find an example of them doing exactly that -- there's prime example [0] right here in this thread!

(Alsa known as "extend"; see also "Active Directory")

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[0]: https://news.ycombinator.com/item?id=25719294