I am using Exchange Server 2007 running on Windows Server 2003 R2 SP2. I have notice very consistent error messages in the applicaiton log of the Exchange server stating the following: Event Type:ErrorEvent Source:MSExchangeISEvent Category:General Event ID:9646Date:8/9/2007Time:8:21:46 AMUser:N/AComputer:%computername% Description:Mapi session " " exceeded the maximum of 32 objects of type "session". For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp. From my investigation I have found various articles that reference this issue on Exchange Server 2003 but not specifically with 2007. The recommended fixes were to either grant "View Information Store Status" to the user or increase the allowed number of mapi sessions allowed by any single user. I am assuming that this issue has to do with my users vpn connection dropping and/or travelling between sitesafter just disconnecting from the network and reconnecting at the next site, while Outlook is still running. That way sessions stay active on the Exchange server. If this is the case then increasing the number of allowed mapi sessions seems to be only a temporary fix being as though eventually they would reach the new ceiling. I also read an article that stated this issue has been noticed on systems using Exchange 2007 while running the Windows Server 2003 Scalable Network pack, which is turned on by default. http://msexchangeteam.com/archive/2007/07/18/446400.aspx. Again, this article references the issue but provides no resolution for Exchange 2007. Has anyone experienced this issue and/or been able to come up with a real resolution on Exchange 2007?

This issue was caused by Windows Scalable Network Service. We ran the following one-liner at the command prompt to solve the issue. Please reference the following article http://msexchangeteam.com/archive/2007/07/18/446400.aspx. Netsh int ip set chimney DISABLED

I know this thread is a little dated; did this fix your issue? I have a similar issue, but before running that command, I found out about a new hotfix from Mircosoft:http://support.microsoft.com/?kbid=948496I installed this update and I will let you know if it helped.Rob

Ialso getting the same issue with exchnage server 2007 CCR withVPN clients. Applying the KB 925815 will it be help/Fix the issue? In LAN enviroument the KB will work. Disanle TCP chimmey will really work? or will it cause more memory(vertual) problam for the server.. Any comments..?

The KB you want is 948496. This is the update that will disable SNP features. I have had this patch on my server for a week now. I still cannot say for certain that the issue is resolved without giving it another week or two, but so far it has not resurfaced. I DID notice that memory utilization is much higher on the server since the update which concerns me. This server houses less than 600 mailboxes and has 8 GB of RAM. Has anyone else experienced high memory utilization after installing KB948496??

I have had the same issue. Try this, and it should help. My system is Exchange SP2 on Windows 2003 SP1 Setting KeepAliveTime to 5 minutes with help with the 9646 session events. How to harden the TCP/IP stack against denial of service attacks in Windows Server 2003http://support.microsoft.com/?id=324270