Running Exchange 2003 SP2 on windows 2003 sp2 + full update.Our store.exe suddenly started to go up to 100% CPU usage for 8-10 minutes every 20-25 minute which stops the outlook-clients to access their mails, mail queue rises and mail correspondance can take from 5-10 minutes where it used to sent the mail within seconds.Checked antivirus, 3rd party services but cannot find the cause - any other ideas out there.

How did you check those services? Did you stop and disable them? When did this start?Anything in the event logs?

I'm monitoring the Tasklist, using ExMon to see the CPU usage. Shutdown/ rebooting the server several times. Tried to stop the AV-services to see if it helped and there is nothing in the eventlog.sadly now when users are back online the store.exe process is back 90-100% more or less constant.Update.The process is now down to more or less normal usage 0-20%. Stopped our Nokia mail system to mobile devices for 1 hour and reenabled it and still steady on the 0-20%.Wonder what caused this and why is it back to normal again.

Hello, You can check with pfdavadmin tool and check the Item count for the users.If users are online and you face this problem i am sure the problem is with the mailboxes connected to the server.There is a limitation for no of items to be present in each folder in the mailbox and if it exceed the recommanded value you may face 100% CPU utilization due to store.exe .So have a look on exmon periodically and pfdavadmin item count and you will be able to fix this issue.Find the step by step procedure with screenshots to check the item count on all the mailboxes using PFDAVADMIN on the below linkhttp://msexchangeteam.com/archive/2007/04/24/438170.aspxAlso, check the recommended item count and also how it will impact the Performance of the exchange server in the below microsoft linkhttp://technet.microsoft.com/en-us/library/cc535025(EXCHG.80).aspx This article clearly explains you about the recommendation about the mobile device connected to the mailbox and i think this will be helpful for you.Thanks,VinodMicrosoft Exchange – Enterprise Messaging Support

The store.exe process is still running normal - but your answer Vinodbabu was quite good with information that could be usefull.The worst part of all this is that I still don't know what caused the high CPU-usage. But it could be the mobile-devices and the exchange needed a break from serving the Nokia DME System.Thank you

I had a very similar problem earlier today. Configuration: SBS2003 Premium (with latest service packs, NO ISA) Server running virtualized on Hyper-V R2, wireless-n access point provides wireless access for mobile devices (WinXP, Win7 notebooks, MACs, iPads and iPod Touch). Store.exe would spike between 95-100% CPU and remain locked for 5-8min, drop and then almost immediately spike again. One thing that we noticed earlier in the day was a user who requested re-configuration of his iPad (IOS 3.2 (7B367)) Exchnage mail (primary) profile because apparently "... mail sync just stopped working" several days ago. Several other Outlook user profiles to same exchange server (on same iPad) have been created but all those seemed fine. When we disabled the main profile sync (made inactive by disabling Mail, Contacts and Calendars) CPU usage dropped back to normal. When only mail sync was enabled (with mail days to sync = 1 day (shortest increment)) everything seemed fine, when turned on to next leven, 3 days, CPU started to spike again. Usage of this iPad is strictly on the lan (local AD and DNS). One other item that was found later during the day is that this user _also_ has a iPhone4 with an Exchange Profile to the same primary account which worked fine. We haven't been able to determine if disabling the exchange profile on the iPhone would permit the one on the iPad to work properly with Exchange.