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Planning for Unity Connection Single Inbox impact on Exchange 2010


With the 8.5 release of the product, Unity Connection introduced the Single Inbox feature. This feature synchronizes voice messages in Connection and Exchange 2010 mailboxes.
The integration with the Exchange 2010 environment is done via the Exchange EWS services.

We now have a whitepaper that describes the performance and Exchange Web Services (EWS) throttling characteristics of the Microsoft Exchange 2010 servers when the Cisco Unity® Connection Single Inbox feature is synchronizing voice messages between Cisco Unity Connection and Microsoft Exchange 2010 on the Exchange 2010 network. Included are the results of performance and EWS throttling tests, a summary of the findings, and recommendations.

This document is provided to help individuals and organizations successfully design, deploy, and maintain Cisco Unity Connection Single Inbox with Microsoft Exchange 2010.

You can download the document here -


Thank you for providing this information.



I need some help here as this document has not been updated with new SP2 RU4 and later changes.  I have a client that cannot remove throttling on every Connection UM user, so we'd like to understand the impact of not doing so and if there are any middle of the road recommendations, short of removing all limits.  It appears that removing the ESW throttling limits is not specific to calls from the Unity Connection Service account, but from any source, and that is what is causing the concern.  Can you please enlighten?

Cisco Employee

Hi Stephanie,

We are in the process of documenting some more specific throttling values rather than out-right turning them off. We also have some improvements (code fixes) for CUC which will help eliminate the need to change/remove some throttling limits. We just received a draft of this last week and are working on finalizing and publishing. I have another customer that is also looking for all of the specifics so give me a couple days to round up all the data and versions and I can post back here with what we will be recommending going forward before it offically gets published.




Thank you so much for the reply. Our project is currently stalled until we can provide a better solution or dataset to the client.


Cisco Employee


Here is the write-up I will be providing to other customers/partners as they inquire until we can get the official documentation updated. Let me know if you have any lingering questions.

Exchange 2010 SP2 Rollup Update 4 and later now calculates usage based on the destination account rather than the source account which is the UM Service Account. Because of the change in where usage is calculated, removing the throttling limits from the UM Service Account no longer affect Unity Connection’s usage of EWS in Single Inbox integrations.

Exchange 2013 and Office 365 Wave 15 use different metrics for throttling and are more relaxed when compared to Exchange 2010 SP2 RU4. As such, the throttling values presented here are not relevant to Exchange 2013 and Office 365 Wave 15 deployments. However, the fix for CSCtz20281 (read further down) improves Unity Connection’s ability to synchronize with larger mailboxes and applies to all versions of Exchange including 2010, 2013, and Office 365 Wave 15.

The following represent the throttling parameters that can affect Unity Connection’s Single Inbox Integration:

  1. EWSPercentTimeInAD - This parameter specifies the maximum amount of time that can be spent by a Client Access server when accessing Active Directory resources on behalf of a client account, per minute.
  2. EWSPercentTimeInCAS - This parameter specifies the percentage of a minute that an Exchange Web Services user can spend executing the client access server code (PercentTimeInCAS).
  3. EWSPercentTimeInMailboxRPC - This parameter specifies the percentage of a minute that an Exchange Web Services user can spend executing mailbox remote procedure call (RPC) requests (PercentTimeInMailboxRPC)
  4. EWSFindCountLimit - Defines the maximum number of items from a FindItem or FindFolder operation that can exist in memory on the Client Access server at one time for one user.

Testing has been performed to help identify proper values for the 4 EWS Throttling parameters that need to be applied to all Single Inbox users within Exchange:

  1. EWSPercentTimeInAD - 100
  2. EWSPercentTimeInCAS - 300
  3. EWSPercentTimeInMailboxRPC - 200
  4. EWSFindCountLimit – 10,000

***Please be aware that these are guidelines for mailboxes with up to 10,000 items in them. Should a mailbox contain more than 10,000 items, then these settings may be insufficient to avoid throttling. The use of Exchange performance counters can be used to help administrators adjust these numbers as required.

During this testing, the development team identified 2 enhancements that could be made to help avoid hitting throttling limits:

  1. CSCtz20281 - Allows Unity Connection to page (group) multiple request together to receive a single response. It also eliminates the need to modify the EWSFindCountLimit parameter which defaults to 1,000.
    1. Patched in 10.0(1), 9.1(2)ES02, 8.6(2)ES, 8.5(1)ES/SU
    2. Exact versions for 8.5(1) and 8.6(2) are not available yet and will be provided ASAP
  2. CSCui39504 - Filters out calendar events from EWS request to reduce responses to Unity Connection.
    1. Fix is not yet available and will be provided ASAP

With the application of these EWS Throttle parameters and versions of CUC that have fixes for the previously mentioned defects, Unity Connection should operate correctly with Exchange 2010 SP2 RU4 and later without completely disabling throttling on user accounts.



This is a great start, thank you very much.  The formal document may be addressing this, but can you please add information about exactly HOW Unity Connection impacts these counters?  The old Unity classic documentation in this area was so much more detailed and the field is really missing that level of information when dealing with our clients.  For instance, you alluded to these new recommendations working well for up to 10,000 items in the mailbox.  From this, I presume that Unity Connection has to open a session against some of these counters for each message or something along those lines.  That level of understanding is what our customers want do know, especially those clients who have to manage 10s of thousands of mailboxes.  They ultimatly want to ensure the stability of their services to their end users.

Thank you,


Cisco Employee

Hi Stephanie,

I may need you to ask more specific questions but I will give it a shot. Unity Connection leverages EWS to constantly synchronize messages and message state between Unity Connection and Exchange. The throttling parameters basically make sure that a specific user does not overload an Exchange server. However, the default values don't allow Unity Connection to synchronize in a timely manner, perhaps you have encounters slow sychronization before? It would more than likely be cased by these throttling thresholds being hit and the synchronization terminated.

In order for Unity Connection sychronize the messages, subscribes to events that it "cares" about in regards to the messages. The processing on these subscriptions and other requests counts against the thresholds that you see above. There can be many simoultaneous connections between a CUC and an Exchange server which is determined by the number of users and the latency between CUC and the Exchange server. A signle user request can use one or more of these simultaneously and this why in Exchange 2010 SP2 RU4, moving the throttling calculations to the ddestination user caused an issue, because before, the throttling was calculated against the source user, which would have been the UM service account (so disabling throttling for this one user allowed us to sychronize as needed without opening the Exchange server up to potential resource issues from the users).

Basically, in Exchange 2010 SP2 RU4, the voice message activity and size of the Exchange mailbox dictate how the the throttle parameters need to be set to ensure that messages and their status synchronize in a timely manner.

If you have more specific queries, just let me know and I will try and get you an answer.

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