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At a customers site with 20+ employees per team I get an outlook warning message roughly translated to "The amount of elements opened at once has been limited by the server administrator".

The customers requirement is that each team member can access the mailboxes of the other team members using "full delegation".

After a quick search I ran into values I need to change in the throttling policy.

In Outlook connection status window I can see that for each mailbox delegation there is at least one new connection created, having 20+ connections on a client. In the protocol column it shows "HTTP" everywhere.

According to microsofts documentation Set-ThrottlingPolicy increased RCAMaxConcurrency and EASMaxConcurrency for Outlook and EwsMaxConcurrency and OwaMaxConcurrency because of outlook connection status protocol column to a more reasonable limit for their case.

My question is: Are those the correct parameters I have to change? Which parameters should I change in such a use case? Am I missing anything?

Silberling
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  • Hi, it's been a long time, is there any update? If the below answers are helpful to you, you could mark the best answer. Have a nice day:-) – Ivan_Wang Nov 25 '20 at 01:49

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Based on your description having 20+ connections on a client. In the protocol column it shows "HTTP" everywhere., your mailboxes should use MAPI over HTTP for Outlook to access Exchange, you could try running the following commands to verify that:

(If the value of CAS mailbox shows blank and the one of organization config shows True, or the value of CAS mailbox shows True, it represents that your mailbox is using MAPI over HTTP)

Get-CASMailbox -Identity <Mailbox Name> | fl MapiHttpEnabled
Get-OrganizationConfig | fl MapiHttpEnabled

For the three parameter RCAMaxConcurrency, EASMaxConcurrency, EwsMaxConcurrency and OwaMaxConcurrency, they are used to specifies how many concurrent connections an Exchange RPC(RPC client access service)/EAS(ActiveSync - Mobie device)/EWS(Exchange Web service, e.g. Outlook for mac)/OWA(Outlook on the web) user can have against an Exchange server at one time.

More details about them: Set-ThrottlingPolicy

For MAPI over HTTP, I think you could try to add a registry key to increase this limit:

Registry Path: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersSystem

Key Name: Maximum Allowed Sessions Per User

Type: DWORD

Value: 21 or larger number

Here is a similar thread for your reference: mapi session(Belinda Ma)

Ivan_Wang
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  • I just ran `Get-CASMailbox | fl Name,MapiHttpEnabled` and got an empty value for that field for each mailbox. For `Get-OrganizationConfig | fl MapiHttpEnabled` i get `True` – Silberling Nov 16 '20 at 11:11
  • @Silberling It means that each mailbox will follow the MAPI setting of your organization, so your mailboxes are using MAPI over HTTP to build the connectivity between Outlook and Exchange Server. – Ivan_Wang Nov 17 '20 at 01:26