I met an interesting issue today during the troubleshooting of an RPC/HTTP connectivity issue on a Windows 2008R2/Exchange 2013 environment.

Observation: The observation was RPC virtual Directory Basic Authentication keeps getting disabled in about 5 minutes even when we enable it manually.  The intermittent observation has noticed during the testing of the RPC/HTTP via http://exrca.com/. It keeps passed when the Basic Authentication keeps enabled and failed when the change has introduced automatically.

Also, the cmdlet output for Get-OutlookAnywhere |fl showed the IISAuthenticationMethods as follows:

So the Exchange was forcefully overwriting the Windows IIS settings for RPC virtual Directory with on some minutes every time.

Requirement:

Default Settings for Exchange Virtual Directories for Exchange 2013 showed the following requirement for RPC Virtual Directory under ‘Default Website’ in IIS

Also IISAuthenticationMethods for OutlookAnywhere should be listed as follows:

How to Fix the issue

The TechNet Blog published here mentioned some hints to fix the issue.

The fix is set the Exchange OutlookAnywhere settings forcefully by using the following cmdlet:

Get-OutlookAnywhere | Set-OutlookAnywhere -IISAuthenticationMethods: Basic, ntlm

After setting this, I have manually Enabled the RPC virtual Directory Basic Authentication and it keeps maintaining the settings because of the fix.

Hope this will help you also !!!!