Testing HTTP Authentication Methods for URL https://mail.ourdomain.com/rpc/rpcproxy.dll?7c29d23d-ce72-44a2-86ba-5fe74d316ace@ourdomain.com:6002.
Additional Details
Not all the required authentication methods were found.
Methods Found: Negotiate
Methods Required: NTLM
I have tried the following on the exchange server
In IIS - under RPC
Change basic to enabled and Windows authentication enabled
Change basic to disable and windows to enabled
change basic to enabled and windows to disabled
I did an IIS reset between each and while the response varied from NTLM or Basic being the issue it fails each time.
I've also tried changing the database from NTLM and basic and likewise with RPC.