In Exchange Server Transport error: 452 4.3.1 Insufficient system resources we learned how the Back Pressure (Previous versions: Exchange 2010 | Exchange 2007) feature monitors resource consumption on Exchange Server and stops accepting new message submission if it’s low on resources.
Update: In Exchange 2013, when the Transport service on a Mailbox server or an Edge Transport server is under resource pressure, incoming connections are accepted, but incoming messages over those connections are either throttled (accepted at a slower rate) or rejected.
Here’s how you can turn off Back Pressure:
- Open the EdgeTransport.exe.config file from \Exchange Server\bin directory using Notepad or other text editor.
- Add the following key+value pair:
<add key=”EnableResourceMonitoring” value=”false” />
- Save the file and then restart the Microsoft Exchange Transport Service (MSExchangeTransport) from the Services console or using the following PowerShell command: