We have an Exchange 2013 Sp1 CU7 server that houses all roles. we configured the mapi virtual directory so that it is using the same name space externally and internally and that namespace is on a trusted certificate installed in Exchange.
We enabled MAPI over HTTP in the org config.
Outlook 2010 SP3 clients are able to create a profile automatically via autodiscover and connect with MAPI over HTTP verified by Outlook connection manager.
Outlook 2013 SP1 clients now prompt for credentials when creating a profile and every time afterwards when opening Outlook.
Both outlook 2013 SP1 and outlook 2010 SP3 clients used to just automatically create a profile based on autodiscover. It seems something is not quite right with authentication on the MAPI virtual directory but I don't understand why outlook 2010 works but 2013 does not. We have NTLM auth method configured on the MAPI virtual directory.