NDRAgent
This sample implements a RoutingAgent. This code executes when the message has been received from the Transport Front-End, put into the queue and is in the process of being categorized by the Hub Transport service.
The purpose of this agent is to drop certain Non-Delivery Report (NDR) and prevent them from being sent to mailboxes. This was originally written to prevent delivery status notification with code "554 5.2.2 mailbox full" to be delivered. It has then been changed to drop (from the transport pipeline) NDR whose message contains "DELETE". This DROP event will appear in the Message Tracking Log as performed by "NDRRoutingAgent".
This Transport Agent implements Event Logging for its operation. This has been chosen at it diminishes the chances of crashing the transport service in scenarios such as when a log file (if logging to text) could be locked by another process (i.e. anti-virus) or not accessible (i.e. missing permissions or non-existing path).
Event Logs would be recorded in the Application Event Log on the server; the agent would try to register a Source matching its name (NDRAgent), if this is not possible it will try to fall back on the DLL name (TransportAgents) and, in case that is not possible as only applications running elevated has the privilege to do so, will fall back to logging entries as "Application" which should be already present and registered.
If you want to make sure the Transport Agent is capable or logging events under its own, separate, source for a quicker identification of the relevant events, please create the source manually on an elevated PowerShell prompt.
This can be done with the following command.
New-EventLog -LogName Application -Source NDRAgent
Alternatively, if you want all different agents to log theri events on a single source, you can create the TransportAgents one as follows.
New-EventLog -LogName Application -Source TransportAgents
- Copy the DLL to the server (i.e. F:\Transport Agents); Make sure the Exchange accounts have access to the folder
- Install the transport agent
Install-TransportAgent -Name NDRAgent -TransportAgentFactory "TransportAgents.NDRAgent" -AssemblyPath "F:\Transport Agents\TransportAgents.dll"
- Enable the chosen Transport Agent
Enable-TransportAgent NDRAgent
- Exit from Exchange Management Shell
- Restart the MSExchangeTransport service
Restart-Service MSExchangeTransport
- Disable the agent
Disable-TransportAgent NDRAgent
- Remove the agent
Uninstall-TransportAgent NDRAgent
- Exit from Exchange Management Shell
- Restart the MSExchangeTransport service
Restart-Service MSExchangeTransport