RPC_NT_SS_IN_NULL_CONTEXT (0XC0030004) fix for admins

You're sitting in the admin console, trying to run a remote PowerShell command or maybe an Exchange Management Shell cmdlet against a server, and boom—you get hit with RPC_NT_SS_IN_NULL_CONTEXT (0XC0030004). It's one of those errors that makes you swear under your breath because nothing obvious is broken.

I've seen this most often in two scenarios: First, when you're trying to connect to an Exchange 2016 or 2019 server from a management workstation and the DCOM call fails. Second, when a scheduled task or script tries to make an RPC call to a remote server but the authentication or impersonation level is off. One specific trigger: an admin tried to run Get-ExchangeServer from a jump box and got this exact code. The DCOM connection to the server's RPC endpoint mapper was handing back a null context handle because the security context wasn't set up right.

Root cause in plain English

The RPC runtime uses context handles to track state between client and server—think of them as session IDs. When the server creates a context handle, it expects that handle to be non-null. If something goes wrong during the binding phase—usually a permissions issue or a misconfigured DCOM launch/access permission—the handle comes back as null. The error code literally means "hey, you passed me a null context handle as an input parameter, which makes no sense."

Under the hood, this is almost always a DCOM security problem. The client either doesn't have the right to launch the server's COM object, or the authentication level is too low. I've also seen it when the server's RPC service is running under a service account that doesn't have the correct impersonation privileges. But 9 times out of 10, it's DCOM permissions.

Step-by-step fix

1. Check DCOM permissions on the server – Open dcomcnfg (Component Services) on the remote server. Expand Component Services > Computers > My Computer > DCOM Config. Find the specific COM class your app is trying to call. For Exchange, it's usually Microsoft Exchange RPC Client Access Service (CLSID {...}). Right-click it, go to Properties > Security tab.
2. Set launch and access permissions – Under Launch and Activation Permissions, choose "Customize" and edit. Add the user or group running the client command (e.g., Domain Admins, or the service account). Grant them Local Launch and Remote Launch rights. Do the same under Access Permissions—add the same group and allow Local Access and Remote Access.
3. Adjust authentication level – Still in the same COM class properties, under General tab, set Authentication Level to "Connect" or higher. Never use "Default" or "None"—that's a common mistake. I always set it to "Packet Integrity" for secure environments.
4. Restart the RPC services – On the server, restart the Remote Procedure Call (RPC) and RPC Endpoint Mapper services. Do this from an elevated PowerShell: Restart-Service RpcSs,RpcEptMapper. This forces a clean DCOM handshake on next connection.
5. Test the connection – From your client machine, run Test-NetConnection -ComputerName ServerName -Port 135 to make sure the RPC endpoint mapper is listening. Then try your original command again.

If it still fails

Alright, you've done the DCOM dance and nothing changed. Here's what else to check:

• Registry hack for null context – On the client machine, open Regedit and go to HKLM\SOFTWARE\Microsoft\Rpc\SecurityService. If you don't see a DWORD named EnableAuthEpResolution, create it and set it to 1. Reboot. This forces RPC to resolve authentication endpoints more strictly, which can flush out hidden null context issues.
• Firewall rules – RPC uses a dynamic port range (usually 49152-65535) plus port 135 for the endpoint mapper. Make sure your firewall isn't blocking those high ports. Quick test: temporarily disable the firewall on both machines (internal network only, not production) to see if the error disappears.
• Service account delegation – If the client is running under a service account, check that it's trusted for delegation in AD. Go to Active Directory Users and Computers, find the account, right-click Properties > Delegation tab, and select "Trust this user for delegation to specified services only." Add the RPC service on the target server.
• Last resort: re-register the RPC libraries – On the server, run regsvr32.exe rpcss.dll and regsvr32.exe rpcrt4.dll from an elevated command prompt. Reboot. I've only needed this twice in my career, but both times it fixed a corrupt RPC registration.

That's the playbook. Start with DCOM permissions, then work through the registry and firewall. This error is stubborn but it's not magic. You'll beat it.