Recently stuck with interesting problem.
Using same credentials with outlook 2010 on Windows 7 and Windows 10 a have different result in autodiscovery.
All working like a charm on Windows 10 and always failing on windows 7 with error 0x800C8203.
At the end i figured that my Exhange 2019 server based on Windows 2019 server, with newest IIS not suppported TLS 1.
And outlook on windows 7 not supporting higher protocols like TLS 1.2
So you have to options how to resolve this probles
1. Add TLS 1.2 support to Windows 7 ( failed for me)
2. Enable TLS 1 suuport on iis with this great software https://www.nartac.com/Products/IISCrypto/
Second option worked for. Yes it is insecure but we have what we have, when deadline already passed :)
