In Exchange 2013 when we run the below can see AutoDiscoverServiceInternalUri
Get-ClientAccessServer | fl AutoDiscoverServiceInternalUri
Normally this should be something like below:
Don’t touch the Autodiscover virtual directory for changing external and internal URI leave it as such.
Their values will be empty and can be checked by running the below command
Get-AutoDiscoverVirtualDirectory -Server servername | fl *url*
Actually there is no ExternalUri we need to specify.
Internally (so when the clients are on the domain and can see the domain) they will query the domain for that value and resolve to it.
Externally the clients go through a pre-set number of URLs:
Then DNS SRV records and finally a redirect.
Therefore for Autodiscover to work correctly externally you need to have one of those URLs resolve and be on the SSL certificate – the most common method is to use Autodiscover.example.com as an additional URL on the UC certificate