Back pressure isn’t only caused by low disk space. Event logs will record back pressure events.

Some more info:
https://www.practical365.com/exchange-transport-server-back-pressure/

Also with Exchange 2013 make sure you’re looking at the correct server role. Transport is on the Mailbox server now, so if you’ve got separate server roles installed then you’ll need to look at your Mailbox not Client Access servers.

I am getting this back-pressure event (452 4.3.1 Insufficient system resources) and inbound (external) email is being delayed.

Both my system (C:) and data (D:) drive have well over 60GB free disk space – yet I keep getting this message.

Any help on where I should look to disable or correct this issue?

Thanks!

Thank you very much for your guidance. I’m able to solve my problem yesterday.

I did a little more Googling on the subject and came across a well informed site at technet; http://technet.microsoft.com/en-us/library/bb125177(v=exchg.80).aspx

There was a Powershell-script for moving what I needed, and everything resolved in a matter of seconds 🙂

My question however is regarding wheter or not I should move the database-files as well? We currently have mail.que of ~340MB and 5MB log/jrs-files in the queue-folder. What services do I need to turn off before being able to move these files, and what are the results of moving/not moving these files?

Thanks in advance for your question, as well as an awesome article really comming in handy 🙂

og Name: Application
Source: MSExchangeTransport
Date: 4/16/2012 3:23:32 PM
Event ID: 15004
Task Category: ResourceManager
Level: Warning
Keywords: Classic
User: N/A
Computer: exserver.domain.local
Description:
Resource pressure increased from Medium to High.

Resource utilization of the following resources exceed the normal level:
Version buckets = 233 [High] [Normal=80 Medium=120 High=200]

Back pressure caused the following components to be disabled:
Inbound mail submission from Hub Transport servers
Inbound mail submission from the Internet
Mail submission from the Pickup directory
Mail submission from the Replay directory
Mail submission from Mailbox servers
Mail delivery to remote domains

The following resources are in the normal state:
Queue database and disk space (“H:Queuemail.que”) = 2% [Normal] [Normal=95% Medium=97% High=99%]
Queue database logging disk space (“H:Queue”) = 2% [Normal] [Normal=95% Medium=97% High=99%]
Private bytes = 3% [Normal] [Normal=71% Medium=73% High=75%]
Physical memory load = 55% [limit is 94% before message dehydration occurs.]

Event Xml:

15004
3
15
0x80000000000000

906
Application
exserver.domain.local

Medium
High

Resource utilization of the following resources exceed the normal level:
Version buckets = 233 [High] [Normal=80 Medium=120 High=200]

Back pressure caused the following components to be disabled:
Inbound mail submission from Hub Transport servers
Inbound mail submission from the Internet
Mail submission from the Pickup directory
Mail submission from the Replay directory
Mail submission from Mailbox servers
Mail delivery to remote domains

The following resources are in the normal state:
Queue database and disk space (“H:Queuemail.que”) = 2% [Normal] [Normal=95% Medium=97% High=99%]
Queue database logging disk space (“H:Queue”) = 2% [Normal] [Normal=95% Medium=97% High=99%]
Private bytes = 3% [Normal] [Normal=71% Medium=73% High=75%]
Physical memory load = 55% [limit is 94% before message dehydration occurs.]

Rajesh, the default threshold is 4Gb. Or at least it was when I wrote this article. I haven’t checked since then to see if a later service pack changed it at all.

Paul my disk had free space of 5 GB but still I was facing issues with inbound mails from external domains, I moved all my data to other server. Now free space was more tha 90 GB.

But how can I know, how much disk space should be retained on disk in future to keep away from problem.

It is really up to you how much you want to tune the back pressure thresholds.

I’m a bit concerned that a 147Gb disk on an Exchange server is full though. What else do you have on that server taking up so much space?