Hi,
Just checking to see if you can get any help from this link:
https://www.msxfaq.de/cloud/sfbonline/hybrid.htm#:~:text=For%20example%2C%20the%20error%20message%20%22404%20Domain%20is%20not%20hosted%20by%20this%20service%22%20in%20the%20first%20line%20says%20that%20the%20domain%20is%20not%20enabled%20in%20Office%20365%20for%20use%20with%20Skype%20for%20Business.%20In%20the%20Office%20365%20admin%20center%20you%20can%20configure%20usage%20per%20domain%20and%20service%3A
Hope the information is helpful.
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