<\/p>\n
xchange Server 2007 Transport: 452 4.3.1 Insufficient system resources<\/h3>\n
by Bharat Suneja on March 25, 2007<\/abbr><\/p>\n In my hotel room in Orlando, getting ready for an Exchange 2007 transport presentation tomorrow morning at TechMentor. When trying to telnet to the SMTP<\/acronym> port of an Exchange 2007 Hub Transport server, I got the following error: <\/p>\n 452 4.3.1 Insufficient system resources<\/p>\n Not a good thing the night before a presentation \u2013 Murphy\u2019s law at work again!<\/p>\n The Application Event Log has Event ID 15002 from MSExchangeTransport saying \u201cThe resource pressure is constant at High. Statistics\u2026 \u201c. The event goes on to tell you that inbound mail submission has stopped, and it\u2019s due to disk space being low on the volume where the queue database is located. Exchange Server 2007 transport queues are not the familiar .eml files you see in Exchange Server 2003\/2000, which reside in the \\mailroot\\vsi <1>\\queue folder (<1> is the instance number of the SMTP virtual server) on the file system. Yes, transport queues have been moved to a JET database of its own.<\/p>\n In Exchange Server 2007, the Transport service monitors system resources such as disk space and memory on Transport servers (the Hub Transport and the Edge Transport servers), and stops message submission if it\u2019s running low on these resources. It continues to deliver existing messages in the queue. When resource utilization returns to normal, it resumes message submission. The feature is called Back Pressure<\/a>.<\/p>\n In this case, Exchange required 4 Gigs of free disk space on the volume where the Queue database was located \u2013 I had about 3.95 Gigs. \ud83d\ude42<\/p>\n The Back Pressure settings in Exchange Server 2007 RTM stop inbound mailflow if free disk space is below 4 Gigs. This static threshold has been lowered in SP1 to a more realistic 500 MB.<\/p>\n Many configuration options for transport servers are saved in an XML file named EdgeTransport.exe.config (it\u2019s the same file name on both server roles\u2014 Edge Transport and Hub Transport) located in \\Exchange Server\\Bin\\.<\/p>\n To get transport to resume submissions, you can use any of the following methods. All of the following require you to edit the EdgeTransport.exe.config file.<\/p>\n![](\"https:\/\/exchangepedia.com\/blog\/images\/EventID15002-MSExchangeTransport.gif\"){kind=spacer}
Figure 1: Event ID 15002 logged by MSExchangeTransport<\/p>\nWhat\u2019s Back Pressure?<\/h4>\n
Changes to Back Pressure settings in Exchange Server 2007 SP1<\/h5>\n
The Resolution<\/h4>\n
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