Exchange Server 2007 Service Pack 2 on Windows Server 2008 Problem: MAD.EXE (Exchange System Attendant) uses 50% CPU =100% of one core 24/7 which makes system sluggish. System Attendant is responsive to Stop and Start requests, but immediate jumps to 50% CPU upon start. The system load is VERY light. I have applied Update Rollup 4 for Exchange Server 2007 SP2: KB981383. "Best Practice Analyzer" are almost clean. Further analysis has shown that it is one thread in MAD.EXE that is acting up: Typical call stack: ntoskrnl.exe!IoAcquireRemoveLockEx+0xe7 ntoskrnl.exe!memset+0x22a ntoskrnl.exe!KeWaitForSingleObject+0x2cb ntoskrnl.exe!KeDetachProcess+0x120d ntoskrnl.exe!PsReturnProcessNonPagedPoolQuota+0x3b3 ntoskrnl.exe!KiCheckForKernelApcDelivery+0x25 ntoskrnl.exe!NtQueryInformationThread+0xfeb ntoskrnl.exe!NtQueryInformationThread+0x1673 ntoskrnl.exe!ZwUnloadKeyEx+0x20d3 ntdll.dll!NtWaitForMultipleObjects+0xa kernel32.dll!FlsSetValue+0x7b3 kernel32.dll!WaitForMultipleObjects+0x11 ABV_DG.DLL!HrStartSubService+0x5946 ABV_DG.DLL!HrStartSubService+0x2e7e MSVCR80.dll!endthreadex+0x47 MSVCR80.dll!endthreadex+0x104 kernel32.dll!BaseThreadInitThunk+0xd ntdll.dll!RtlUserThreadStart+0x21 ABV_DG.DLL should be "Recipient Update Service (RUS)", but I have no idea what it is. Problem started after SP2 were applied.

Hi Philip, Please have a look of similar thread for help ! http://social.technet.microsoft.com/forums/en-US/exchangesvrgeneral/thread/63f8ceee-6769-4471-a46d-c2efa9d55700 Anil

Thanks, but I found that article long before posting here. Unfortunately it didn't help and in fact didn't help the original poster either.

Are there really nobody who knows what "Recipient Update Service (RUS)" is?

Hi, Sorry for late response !, There is no use of RUS now in exchange 2007 and it was part of legacy exchange 2003 server. http://msexchangeteam.com/archive/2006/10/02/429053.aspx For your actual issue. Dis you installed any AV software like trend etc if yes then please disable and check it. also i suggest you to take one reboot of DC which is connected with exchange (I know its not much recommended) in non business hours. Waiting for your comemnents !Anil

Hi, Oops! My mistake! ABV_DG.DLL is actually: "Address Book View and Dynamic Groups Service". There is no AV installed on that particular server, and servers has been restarted several times last night.

Hi, Testing the problem in clean boot mode to determine if the problem is caused by third-party services or startup items: http://support.microsoft.com/kb/331796

Hi, When I first saw the article you linked to, I thought you must be slightly mad... (he he) But I gave it a go. As there are almost nothing on that machine besides Microsoft stuff and the APC (battery backup) service, it was quickly done. Unfortunately, it didn't change anything. Baaaah! This is driving me nuts!