Tuesday, June 8, 2010

Client Throttling policies in Exchange 2010

Last week we had two clients complaining about various issues regarding connectivity to the Exchange 2010 Client Access server from various sources:

- Error when activating new devices in Blackberry Enterprise Server with the following info:

[20400] (01/13 15:27:09.003):{0x21AC} {email@address.com} MAPIMailbox::MAPIMailbox - OpenMsgStore (0x8004011d) failed, MailboxDN=/o=CGP/ou=First Administrative Group/cn=Recipients/cn=SERVER, ServerDN=/o=AD/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Configuration/cn=Servers/cn=SERVER/cn=Microsoft Private MDB

[40720] (01/13 15:27:09.003):{0x21AC} MAPI call failed. Error 'The information store could not be opened.', LowLevelError 0, Component 'MAPI 1.0', Context 649

You can find the solution published on the Blackberry support site: http://www.blackberry.com/btsc/search.do?cmd=displayKC&docType=kc&externalId=KB20608


- Error when accessing the Exchange Management Shell or Exchange Management Console with the following info:

The WS-Management service cannot process the request. The user load quota of X requests per Y seconds has been exceeded. Send future requests at a slower rate or raise the quota for this user. The next request from this user will not be approved for at least Z milliseconds.

You can find the solution here: http://www.c7solutions.com/blog/

Both issues were related to a new feature from Exchange 2010 called “Client Throttling”. Client throttling policies control the performance of the Exchange Server infrastructure by tracking the resources used by each user and limiting connection bandwidths as necessary. The feature controls the resources access by component basis. The following clients are controlled by the policies:
- Microsoft Exchange ActiveSync
- Exchange Web Services
- Outlook Web App
- IMAP4
- POP3
- PowerShell
- Unified Messaging (UM)

The problems that we encountered were generated by the default policy for Client Throttling. For common Exchange installations this policy does not generate problems but there are installations, usually large installations, with many clients, that may generate issues.

To find out what is the default Client Throttling policy you may run the following command
Get-ThrottlingPolicy | Where-Object { $_.IsDefault –eq $true }

You can find more info about this new feature and how to set it up correctly on the Technet site http://technet.microsoft.com/en-us/library/dd297964.aspx