I have set up email autodiscovery on a non-Exchange email server per [this technet article], and when testing with Outlook 2015, it does not work.
Outlook hits the server multiple times, retrieving autodiscover.xml from example.com, autodiscover.example.com as well as the same but with passing the user's credentials via HTTP AUTH headers. So it seems to be retrieving the xml file but does not like the contents thereof.
I also used the [Microsoft testing tool] and passed the "Outlook Autodiscover" test, but not the "Outlook Connectivity" test, which may also indicate that my xml is bad, but the latter may only work if you point to an Exchange server, which is not the case here.
I followed the [instructions] carefully, so I am wondering if Microsoft has updated Outlook's autoconfiguration protocol or broken it somehow with non-Exchange servers?