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Event 9646 Exceeded maximum objects of type "session"

Event 9646 Exceeded maximum objects of type "session"

Event 9646 Exceeded maximum objects of type "session"

I've read MS KB Article: 830829 and changed the regsitry with the following value:

\\HKEY_LOCAL_MACHINE \SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersSystem\MaxObjsPerMapiSession

DWORD: session
Value: 128 (decimal)

Rebooted the server and I am still getting users unable to connect to the Exchange server, after this event is logged.
The event still states:

Mapi session "/o=Reid Farmers Ltd/ou=Head Office/cn=Recipients/cn=rfinch" exceeded the maximum of 32 objects of type "session".

So it seems the registry key has not increased the limit from 32?

The KB article refers to Object Types starting with "Obj" e.g objtMessage 250 250
objtFolder 500 500
objtAttachment 100 500

But no mention of session.

Can anyone help me here?
Am I changing the correct registry value?
How do I make this go away?


RE: Event 9646 Exceeded maximum objects of type "session"

Ideas/ guesses all welcome

RE: Event 9646 Exceeded maximum objects of type "session"

Well, something on the client side is opening more than 32 sessions.  It could be a bug in a mapi client, or a poorly designed application or addin, or just plain abusive user behavior.  In order to get this particular error you're at SP1, where the limit was set to 0x20.   

First, realize that each open session consumes virtual memory.  Check your virtual memory perfom counters to ensure that you are not headed for a crash.

Next go download the Microsoft Exchange Server User Monitor so that you may investigate the client behavior.


After that, if it appears to be a client addin or application doing silly things like launching new sessions to check the status of the message store (wonder what app that would be) you could grant "view information store status" permission to the account.

Next, visit the user to see if they're doing dumb things like opening 32 additional mailboxes or other user's calendars at the same time.  Maybe a behavioral modification and a little user education could resolve your issue.

If it's a flakey application, contact the vendor to see if there are any fixes or patches available.

If all that fails, and you're not running low on virtual memory, maybe, just maybe, you might slip by by adding the following registry value to raise the limit:


dword value - Maximum Allowed Sessions Per User

you might have to create it if it doesn't exist.

the default is 0x20.  You could raise it, but if you go too high you risk causing virtual memory issues.  I'd only do this as a last resort.

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