Over the past week or so we have been tracking sporadic complaints about mail delivery delays to Exchange 2007 hosting. It appears that in rare cases the Exchange 2007 network temporarily rejected the message with a 4.3.1: Insufficient system resources message even though plenty of resources were available on the system to process the message and plenty of storage was available on the volume. We have seen this issue creep up from time to time on multiple Exchange 2007 issues and have provided information to Microsoft regarding a possible bug but have so far been unsuccessful in getting a response because the issue is so sporadic that it cannot be pinned down to a single factor and only a small number of messages encounters an issue. What is even more frustrating is that even during heavy maintenance and optimization tasks the issue does not creep up where it is expected with back pressure controls. This Sunday we ran a database optimization maintenance process and out of roughly 1,000 messages processed less than 20 were deferred with the Insufficient system resources error even though the CPU utilization was above 80%. Due to the level of complaints and our inability to isolate this issue with Microsoft we have disabled the back pressure feature of Microsoft Exchange 2007 on all our systems until further notice. Further details about Exchange 2007 and back pressure is available at Microsoft TechNet. Note: This issue is isolated to the new feature in Exchange 2007 called back pressure. Exchange 2003, ExchangeDefender and ExchangeDefender LiveArchive are not affected by this issue. |
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