How to turn off Back Pressure on Exchange Server

by Bharat Suneja

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:

  1. Open the EdgeTransport.exe.config file from \Exchange Server\bin directory using Notepad or other text editor.
  2. Add the following key+value pair:

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

  3. Save the file and then restart the Microsoft Exchange Transport Service (MSExchangeTransport) from the Services console or using the following PowerShell command:

    Restart-Service MSExchangeTransport

{ 6 comments… read them below or add one }

Ben Winzenz March 29, 2007 at 3:50 pm

This is good information, but it really should be stressed that turning off back pressure is not recommended. It is enabled so that Exchange can detect and prevent problems. More information on Back Pressure can be found here:


Bharat Suneja March 29, 2007 at 6:17 pm

Certainly, it’s not recommended to turn off Back Pressure – it’s one of the smarter things Microsoft has done with Receive Connectors (aka “SMTP virtual servers” in previous versions), and the transport.

Back Pressure parameters can be tweaked, as mentioned in the earlier post linked in the above one.

Nevertheless, this comes in handy when you want to turn on transport/message submission asap – as the last option perhaps.



dabash March 15, 2010 at 4:46 am

thanks for you its really nice trick , i use it today until i manage to clean hard disk , so users did not feel there is any email blocked
after i clean the hard disk i return the EdgeTransport.exe.config file as before

thanks again


Patrick Feller October 28, 2010 at 2:39 pm

I had this same issue but when I backed up the exchange database it cleared the logs and the transport service was then able to start normally.


rawbar January 1, 2012 at 9:20 am

I just had to turn this off myself, but I don’t see anything wrong with the server as far as resources go. Exchange 2010 is running in a Hyper-V VM, but CPU, memory and disk space are all good.


rawbar January 1, 2012 at 9:54 am

Update: Found this digging through the event log
The following resources are under pressure: Queue database and disk space (“C:\Program Files\Microsoft\Exchange Server\V14\TransportRoles\data\Queue\mail.que”) = 97% [Medium] [Normal=95% Medium=97% High=99%] Queue database logging disk space (“C:\Program Files\Microsoft\Exchange Server\V14\TransportRoles\data\Queue\”) = 97% [Medium] [Normal=95% Medium=97% High=99%] The following components are disabled due to back pressure: Inbound mail submission from Hub Transport servers Inbound mail submission from the Internet Mail submission from Pickup directory Mail submission from Replay directory Mail submission from Mailbox server Mail delivery to remote domains Loading of e-mail from the queuing database (if available) The following resources are in normal state: Version buckets = 0 [Normal] [Normal=80 Medium=120 High=200] Private bytes = 0% [Normal] [Normal=71% Medium=73% High=75%] Physical memory load = 29% [limit is 94% to start dehydrating messages.] Batch Point = 0 [Normal] [Normal=1000 Medium=2000 High=4000] Submission Queue = 0 [Normal] [Normal=1000 Medium=2000 High=4000]


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