Event 9646, MSExchangeIS - Mapi session exceeded the maximum - Exchange 2010 SP1

Posted on 2011-03-11
Medium Priority
Last Modified: 2012-06-27
Based on the older version of this article here:


I created the ParameterSystem Subkey, with the Maximun Polling Frequency key and set the Decimal value to 45000.
This was to mitigate the delay issues in Outlook 2003.
Ever since then I receive this error message in my event viewer.

Event 9646, MSExchangeIS

Mapi session "13fbc88b-c9fc-4b9c-9efd-14de7957eee4: /o=MYDOMAIN/ou=First Administrative Group/cn=Recipients/cn=MYUSER" exceeded the maximum of 32 objects of type "session".

Another user get this:

Mapi session "2e5673f1-a3bd-4d56-b988-03c1267012b2: /o=MYDOMAIN/ou=First Administrative Group/cn=Recipients/cn=MYUSER" exceeded the maximum of 250 objects of type "objtMessage".

I have received about 6 of these.

I'm not saying this started as a result of me creating the subkey...Microsoft would have to confirm that.
I'm just saying that this is when I started to notice it.

My system specs are:
Exchange 2010 SP1 Enterprise - Update Roll Up 2
Windows Server 2008 R2 - All updated up until December 12, 2010.

Any ideas?
Question by:Treadstone21
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Expert Comment

ID: 35112612
I am not sure about Exchange 2010, but in earlier versions there was a limit on the maximum number of objects a mapi session could have open with the Exchange server, such as 250 messages (as in your error above). I think there was a registry key you could change (escapes me at the moment) which increases this, but you have to way up the pros and cons of having more connections to Exchange and system performance. If you google the error I am sure it will give you a the reg work around. If this is nothing to do with the change you made, you may want to check why that session has so many connections open.

Author Comment

ID: 35113000
How can I verify that?

Expert Comment

ID: 35113202
use exchange management shell and type: get-logonstatistics "username" |fl

In 2007 this would tell you how many folders were open, how many messages...

Sorry but I am a bit flakey on 2010, but I am sure it will be very similar.
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Author Comment

ID: 35113243
Should be, I'll check thanks!

Accepted Solution

Treadstone21 earned 0 total points
ID: 35453883

Author Closing Comment

ID: 35481756
This resolved my issue.

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