"452 4.3.1 Insufficient system resources" error message from Exchange

What the message means:

This error message is generated by Exchange and just relayed by POPcon. With this SMTP error message Exchange is telling us that no new emails are accepted because the harddisk space is less than 4GB.

This is a MS TechNet article on the Exchange feature: Back Pressure.

Not sure if it's a good idea but one user found out that it is possible to turn off backpressure totally: Open the EdgeTransport.exe.config file from \Exchange Server\bin directory using notepad and change <add key=”EnableResourceMonitoring” value=”true” /> to value false. Then restart exchange transport service.

What you need to do now:

Clear disc space for Exchange to accept new emails again.
Move the email files from the BADMAIL folder to the PICKUP folder (both in the c:\program files (x86)\POPcon folder) to have them resent to Exchange.

How to make sure this never happens again:

Check out our new product ServerPulse. ServerPulse monitors your server and immediately sends you a text message to your mobile phone and an email if the server is down and (more importantly in this case) also warns you when the harddisk is nearly full. So you can move and make more room before Exchange stops receiving emails!