SenderDomainRewriteAgent
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.
This Transport Agent has the purpose of changing on the fly a domain that is no longer in use with one that is being used instead. In the sample you'd see the old domain to be "contoso.com" while the new domain to be used will be "tailspin.com". This could be for example the case of an organization changing domain and having line of business applications that still send with the old domain and are yet to be reconfigured.
It must be noted that the sample code checks for the sender domain and not the recipient domain, however the same same logic could be applied to change the recipient domain.
The agent would inspect both the P1 (SMTP envelope) and the P2 (Message) and amend the domain as needed, unless the sender belongs to the list of "excludedFromRewrite".
The scenario covered here is complemented by the RecipientDomainRewriteAgent.
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 (SenderDomainRewriteAgent), 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 SenderDomainRewriteAgent
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 SenderDomainRewriteAgent -TransportAgentFactory "TransportAgents.SenderDomainRewriteAgent" -AssemblyPath "F:\Transport Agents\TransportAgents.dll"
- Enable the chosen Transport Agent
Enable-TransportAgent SenderDomainRewriteAgent
- Exit from Exchange Management Shell
- Restart the MSExchangeTransport service
Restart-Service MSExchangeTransport
- Disable the agent
Disable-TransportAgent SenderDomainRewriteAgent
- Remove the agent
Uninstall-TransportAgent SenderDomainRewriteAgent
- Exit from Exchange Management Shell
- Restart the MSExchangeTransport service
Restart-Service MSExchangeTransport