When trying to open Microsoft Dynamics CRM Client for Outlook or when you try the offline synchronization process in the Microsoft Dynamics CRM client for Outlook with offline access you might experience errors like the following:

  • Outlook becomes unresponsive (flashing) and you have to terminate the process

Outlook will show an Error: There was no endpoint listening at net.pipe://localhost/WebFormService/{random-guid-number} that could accept the message. This is often caused by an incorrect address or SOAP action. See InnerException, if present, for more details.


CRM client for Outlook leverages Windows Communication Foundation (WCF) to communicate with an off-process service to interface with CRM server. The WCF binding used is net.pipe which has a very particular way of naming the underlying named pipe. Starting with WCF 4.0, The process of naming and registering the URI of the net.pipe endpoint is hierarchical and in two levels: non-administrative mode and administrative mode. If a process register the URI net.pipe://localhost, all non-administrative processes will not be able to access any other service with net.pipe binding including net.pipe://localhost/WebFormService/{random-guid-number} which is the CRM local Web Form Service signature.


There is no solution as this is by design. WCF Services should not have a listener URI at net.pipe://localhost/. However there are two workarounds if the situation is true.

To find out which process is holding the listener at net.pipe://localhost/ follow the steps below:

  • Unzip into a folder (e.g: c:\sysinternals)

  • Open cmd.exe as Administrator

  • Move to the folder where you unzipped Handle.exe (e.g. cd c:\sysinternals)

  • Run this command:

handle "net.pipe:EbmV0LnBpcGU6Ly8rLw=="
  • If there is a match, it will tell the executable name and PID as the sample output below:

StandAloneService.exe pid: 10724  type: Section   318: \BaseNamedObjects\net.pipe:EbmV0LnBpcGU6Ly8rLw==

Workaround 1

Find the file (or service) listening to net.pipe://localhost as specified earlier and stop it while you run Outlook.

Workaround 2 (less recommended)

If you launch Microsoft Dynamics CRM Clients for Outlook with local admin rights (right-click on Outlook and select Run as Administrator), the Microsoft Dynamics CRM Client for Outlook works as design and you can use the offline synchronization process with no errors.

More Information

Named Pipes in WCF are named but not by you (and how to find the actual windows object name)

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