SMTP Error: 452 4.3.1 Insufficient system resources

452 4.3.1 Insufficient system resources

This error can be somewhat confusing as when looking at your Exchange server all appears to be well in the world.

What this error actually means is that a feature called ‘Back Pressure’ has been invoked.

Back Pressure was introduced in Exchange 2007.

It is designed to protect the Exchange server from encountering situations where disk space completely fills up and the server cannot continue to function. A kind of “self protection” system.

If your in this situation, chances are you are getting shouted at and need to get email flowing again, and FAST !

A workaround is shown below – note – this is NOT a solution, you will need to fix the disk space permanently or else you will find yourself with zero free space – not good.

navigate to /program files/microsoft/exchange server/v14/bin

find the file EdgeTransport.exe.config and edit with notepad

change the line

<add key=”EnableResourceMonitoring” value=”true” />

to read

<add key=”EnableResourceMonitoring” value=”false” />

Save and close the file.

Restart the Microsoft Exchange Server Transport Service

Email flow will now be restored.


If you need help or guidance with your Exchange server, contact us today.