Deutsche Telekom. I also remember it being stopped, but looks like it has been revived.
This sounds as if Microsoft would not have access to data, which is managed by T-Systems independently. But there might of course be something in the fine print.
My browser is set to prefer English, cookie banners etc. are working, but the rest of the site won't switch, cannot find a button to manually switch either.
[0] https://geschaeftskunden.telekom.de/digitale-loesungen/softw...