This error is related to Microsoft Exchange Servers only.
A routing error.
Also, like most other Microsoft Errors, this message leaves a lot to question. No official description is provided for this, however see the fix suggestion for possible further diagnosis.
Microsoft's official suggestion for diagnosing and attempt to resolve the issue, is to use their WinRoute tool. You can see more on this in their official knowledgebase here: Microsoft KB: How to use WinRoute tool