We are seeing Outlook clients ends up building many connections to the back-end server. In some cases single Outlook client establishes hundreds of connections with no RPC traffic flowing through these connections for hours. Note that Outlook connections are intercepted by third party proxy devices.
Exchange 2010 is used in back-end server which is accessed by Outlook 2007/2010 applications.
Few characteristics observed during incident:
- Lots of Outlook clients reached their maximum concurrent connection limit configured on Exchange Server
- Number of Outlook established connections matched with the those handled by Proxy device indicating that the connections were initiated by the client and not the Proxy.
- Also when one of stale connections are closed by force, Outlook application immediately closed all other connections.
The questions we are trying to answer:
- If maximum connection limit to the Exchange server is reached, why does Outlook client is still opening more connections?
- Why Outlook does not close stale/non used connections?
- Is there a debug level event logs that would help us to troubleshoot Outlook and Exchange server behavior for this type of incident?
Janis