There are several causes of the error “Your computer can’t connect to the remote computer because the remote desktop gateway server is temporarily unavailable” in Windows SBS 2011. There are a lot of articles that deal with the specifics so I’ll go over those more common causes briefly before explaining my issue (which related to uninstalling Exchange).

Common Causes of RD Gateway Unavailable on SBS 2011

In my case, none of these were the cause.

Missing Assembly After Exchange Uninstall

I uninstalled Exchange Server from SBS recently (this company migrated to Office 365 and we wanted to remove the Exchange attributes from their Active Directory), and the RD Gateway doesn’t get much use so I didn’t immediately make the connection. I found it after I checked the Application Event Log. It showed a Warning event 1310 from ASP.NET. The event detailed an Exception as follows:

Exception information:
Exception type: ConfigurationErrorsException
Exception message: Could not load file or assembly ‘Microsoft.Exchange.RpcClientAccess.Coexistence, Version=, Culture=neutral, PublicKeyToken=31bf3856ad364e35’ or one of its dependencies. The system cannot find the file specified.

When I checked the web.config file for /Rpc I saw that it was referencing the assembly in Exchange’s bin directory, typically located here:

C:\Program Files\Microsoft\Exchange Server\V14\bin

Sure enough, there were files leftover, but the referenced file was not one of them. I did a search on the drive and found the missing file in the setup files for Exchange 2010 SP3. I ended up copying every file named Microsoft.Exchange.RpcClientAccess*.dll to the bin directory, did an iisreset, and it worked from there. The source for the files within the service pack setup is:


If this helped you, please let me know!