Exchange 2016 doesn't display OUs in EAC

I ran into this same issue and got tired of manually re-applying the web.config fix after every cumulative update, so I automated it.

The problem is that Exchange CUs overwrite the web.config file and remove the GetListDefaultResultSize key every time. I created a PowerShell script with a scheduled task that:

Checks the ECP web.config for the GetListDefaultResultSize key

Adds it automatically if missing or updates the value if too low

Creates timestamped backups before making changes

Restarts the MSExchangeECPAppPool to apply the fix

Runs daily so you never have to manually fix this post-CU again

GitHub repository: https://github.com/digitron64/ECPFix

Works on Exchange Server 2013, 2016, 2019, and Subscription Edition (SE). Must be deployed to all Exchange servers with the Mailbox role since ECP requests can hit any server in the environment.

The repo includes the PowerShell script and pre-configured scheduled task XML. Tested and working across our three-server environment.

Hope this helps!

Hi @Gregor Jus ,

From your description, my understanding is you have modified the web.config file on the new Exchange server only, and would like EAC to display all OUs only when accessing this particular new server, right?

I tried to test in my lab which has multiple Exchange servers and it seems to me that it can work as expected:

1. In my test lab which has one Exchange 2010(exch2010), one Exchange 2013 (exch2013) and one Exchange 2016 (exch2016), I modified the web.config file on the exch2013 only, verified it worked when accessing https://localhost/ecp on the Exchange 2013 server.
2. Then I tried accessing https://exch2013/ecp/?ExchClientVer=15 on another server(exch2016), it also worked, while https://localhost/ecp or https://exch2016/ecp/?ExchClientVer=15.1 still not work .

So from my test result, my assumption is that it should work when you try to access the particular new Exchange server.

May I know if you have tried on a few more machines to see if there's any difference?
And how about using the IP address of the new server and see if there would be any difference, like https://newserverip/ecp?

--
Update:
Test procedure with two Exchange 2016 servers (e16a and e16b):

"a" is an admin account whose mailbox is hosted on the mailbox database on e16a,
"b" is an admin account whose mailbox is hosted on the mailbox database on e16b.

1. On e16a, added <add key="GetListDefaultResultSize" value="2" /> into the web.config file on e16a, which means allow only 2 OUs to show up, restart the MSExchangeECPAppPool application pool.
2. On e16b, added <add key="GetListDefaultResultSize" value="10" />, restart the MSExchangeECPAppPool application pool.
3. Access as user "a" to https://localhost/ecp and https://servername/ecp on both servers, only 2 entries are displayed, which means it's the configuration on e16a that takes effect.
4. Login as user "b" to access https://localhost/ecp and https://servername/ecp on both servers, 10 entries can show up, which means it's the configuration on e16b, where b's mailbox is located, that takes effect.

So it seems that the it's related to where the admin account's mailbox is hosted.

As regards to the test result in the coexistence lab I mentioned earlier, feels it could be that things are different in coexistent environment and also the admin account I used is hosted on Exch2010.

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