The issue is that the outlook client (tried both 2016 and 2019) refuses to gather response information - let's say - for 9 times of 10, as it would be wrong somehow, even there are access logs of my apache webserver, showing proper responses (code 200). Furthermore - outlook also provides a tool to test if the autodiscover configuration is proper on specified domain (Test Email AutoConfiguration in tray) and that kind of test is always being passed (the difference here is that on the first scenario requests are coming from some MS network and the Test Email AutoConfiguration always comes from the local machine). Is there any reasonable explanation for such behaviour?
I'm not really convinced if my question matches exactly this hub, but I hope it does. Any help would be really appreciated.