Outlook 2016 Credential Popup and Does not work on Domain Network

Question

We are going through migrating users from Office 2010 to Office 365. We have a on-prem 2010 exchange server and will be using the exchange cloud via O365. We have only migrated over 5 users and are doing the hybrid process. We are currently running into a few issues (specifically on the domain network) with Outlook 2016 and Skype currently. First, Outlook continues to prompt credentials constantly unless we add the following registry keys.

[HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover]
"ExcludeScpLookup"=dword:00000001
"ExcludeHttpsRootDomain"=dword:00000001
"PreferLocalXML"=dword:00000001
"ExcludeHttpsAutoDiscoverDomain"=dword:00000001
"ExcludeHttpRedirect"=dword:00000001
"ExcludeSrvRecord"=dword:00000001
"ExcludeExplicitO365Endpoint"=dword:00000001
"ExcludeLastKnownGoodUrl"=dword:00000001

[HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover\RedirectServers]
"autodiscover-s.outlook.com"=hex(0):
"autodiscover-s.partner.outlook.cn"=hex(0):
"autodiscover-s.outlook.de"=hex(0):
"autodiscover-s.office365.us"=hex(0):
"autodiscover.hotmail.com"=hex(0):
"TestDomain.com"=hex(0):

[HKEY_CURRENT_USER\Software\Policies\Microsoft\office\16.0]
"PreferLocalXML"=dword:00000001
"ExcludeHttpRedirect"=dword:00000001
"ExcludeHttpsAutoDiscoverDomain"=dword:00000001
"ExcludeSrvRecord"=dword:00000001
"ExcludeExplicitO365Endpoint"=dword:00000001
"ExcludeScpLookup"=dword:00000001
"ExcludeHttpsRootDomain"=dword:00000001
"ExcludeLastKnownGoodUrl"=dword:00000001

Having these keys or at least some of them, prevent the credentials to constantly show. On the other hand, our Skype for Business application says "Exchange needs your credentials. Until then, you might see outdated info in Skype for Business" in a yellow bar that allows me to enter my credentials but does not make a difference. What I did to fix this skype issue is to add our autodiscover that points to our on-prem exchange server in my hosts file on my computer. After doing this my EWS URL's for internal and external in Skype for Business show up and Skype works fine.

Another issue we have in Outlook is Public folders and shared mailboxes do not show unless I connect to an internet source outside of our domain network. Once i disconnect from our domain network and connect to our wireless internet, I instantly get my shared mailboxes and public folders. Our public folders are on the on-prem exchange server as well.

We have works closely with our Dell rep support and they even brought in a Microsoft rep (who gave us the registry entries). We recently got a SAN certificate and updated accordingly (unless there is a mistake within the certificate), and have whitelisted a ton of IP's and FDQN's (which should not make a difference because i do not see any issues in my packet filter on my sonicwall). When they confirmed that it works fine outside of our domain network, they booted us and stated we need to pay Microsoft to look at our network. I have searched to the ends of earth in forums and other articles for this issue but have not found any fix yet. Anyone have similar issue or possible causes?

Answer 1

In regards to the prompting credentials, I believe that is due to the IIS virtual directories settings with Autodiscover & EWS.

Make sure to

• disable Anonymous authentication
• enable Kernel-Mode Authentication (in advanced settings)

and restart IIS.