Ever see this error when you try to modify members of a large (1000+) member DL using Outlook when your mailbox is on Exchange 2010?
"The public Group cannot be displayed. The operation failed"
"The public group cannot be displayed. Too many names have been found in the directory service or the server has exceeded its time limit for searching. Type more letters of the name and try again"
If you clear this error, you may see a partial list of the DL members displayed. You will be able to successfully add members to the DL. You will also be able to remove members, if they managed to make it in the partial list.
Poking around in the application log of the Client Access Server you are connected to shows nothing out of the ordinary…even if you ramp up diagnostic logging.
The reason this error pops up, and the reason why nothing is logged, is because the CAS is doing exactly what you told it to do. Well…to be fair…it is doing exactly what its default settings told it to do. It is throttling your connection.
The specific throttling policy parameter that relates to this is RCAPercentTimeInAB. By default, this parameter is blank in the Default Throttling Policy that ships with Exchange 2010. If I am reading TechNet right, blank mean default and default maps to a setting of '5'. For all of these *PercentTimeIn* parameters, the number indicates what percentage of a minute you can use in that minute. '5' would therefore equate to 3 seconds (5% of 60 seconds). If you use your budget of 3 seconds, you need to wait for the minute to roll over to get a new 3 second allocation. Outlook is not that patient (nor are most end-users) and blows the error above.
I have found that a setting of 20 (which would equate to 12 seconds) is adequate for most deployments, but your needs could differ. I highly recommend experimenting with this setting on a "test" throttling policy that you apply to a few test users before you roll anything into the default policy.
For more details on creating and setting Client Throttling Policies, see Understanding Client Throttling -- TechNet
If you are using Outlook 2010 and the DL in question is 5000+ users, you may also see this error when you try to look at the properties of the DL:
"Unable to connect to retrieve additional data"
To fix this one, you need an update to Outlook to get rid of a hard coded limit of 500 DL members.
This fix was delivered in the April 24, 2010 Outlook 2010 hotfix package