The Exchnage server prompts the following error:Data : {91, 68, 73, 65...}Index : 268496Category : GeneralCategoryNumber : 6EventID : 9646EntryType : ErrorMessage : Mapi session '/o=WDW/ou=XXXX/cn=Recipients/cn=xxxxxx' exceeded the maximum of 500 objects of type 'objtFolder'.Source : MSExchangeISReplacementStrings : {/o=WDW/ou=XXXX/cn=Recipients/cn=xxxxxx, 500, objtFolder}InstanceId : 3221628334TimeGenerated : 11/24/2009 9:17:33 AMTimeWritten : 11/24/2009 9:17:33 AMUserName : Site : Container : When I run the mailbox statistics of this mailbox, this mailbox does not contain more than 500 folders. It only contians 20~30 folders and each of these folders only contains less than 500 messages. As well, no sepcial add-in is added to the Outlook client.So, what does the 'objtFolder' refer to? Number of total folders in a mailbox? Or else?

Have seen this multiple times. Changing the registry key HKEY_LOCAL_MACHINE \SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersSystem according to this KB http://support.microsoft.com/?kbid=830829will help. But also check if this person is accessing any shared mail box and also any automated series of emails.Raj

Hi Raj,Thanks for your reply. Yes, I can change this key. But my question is what the number of 'objtFolder' refers to.When I run the mailboxstatsics of the user's mailbox that reported to have issue, belowshows the result. Neither exceeding number of folders nor exceeding number of items is found in the emailbox.Identity ItemsInFolder-------- -------------/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 254/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 222/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 143/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 92/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 53/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 52/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 31/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 26/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 24/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 16/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 15/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 14/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 14/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 14/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 14/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 10/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 9/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 6/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 6/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 4/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 4/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 1/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 1/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 1/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 1/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 1/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 1/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 1/o=YYY/ou=XXXX/cn=Recipients/cn=xxxxxx\0/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 0/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 0/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 0/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 0/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 0/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 0/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 0/o=YYY/ou=XXXX/cn=Recipients/cn=xxxx... 0

Its not about the number of items in the folder. See the explanation here http://support.microsoft.com/?kbid=830829Raj

I wouldn't just go changing the registry key as this is simply masking the problem. Go to the user in question and see what they're doing. Last time we saw this it was due to the user's Outlook client having the "download shared folders" option enabled like Raj said earlier, causing shared mailbox contents being downloaded locally. Also, the other thing that often causes this is when the user has 3rd party desktop search programs enabled, hammering the server, etc.Neil Hobson, Exchange MVP

Yep, and you can use Exmon from the server to get a realtime view of the connections as well:http://www.microsoft.com/downloads/details.aspx?FamilyId=9A49C22E-E0C7-4B7C-ACEF-729D48AF7BC9&displaylang=en