Change Outlook Anywhere Authentication

Question

Hello experts,
We have an Exchange 2010 environment and all clients are connecting using Outlook Anywhere. By All I mean all clients inside the network, outside the network, domain joined, so all.
Following is the Authentication settings on Outlook Anywhere.
ClientAuthenticationMethod      : Basic
IISAuthenticationMethods        : {Basic}
I want to change all users to use NTLM, so no more password prompts. I want to reduce the impact because we have more than 10k clients. Based on my understanding, I am planning below approach. Any suggestion will be appreciated.
1. Change the IISAuthenticationMethods to have both Basic & NTLM using set-outlookanywhere command. This will allow clients to use both Basic & NTLM and we can do tests from all locations if its working without any issue.
2. Chang the ClientAuthenticationMethod to NTLM, so Autodiscover will update all existing and new clients to use NTLM.
3. Modify any GPO if in place to change the Outlook authentication to NTLM.
Anything else which need to be taken care of. Many thanks for any suggestions in advance.
-V
-V

Answer 1

Hi,
To make Outlook client use NTLM authentication, I recommend you use the command set-outlookanywhere to change the authentication method. Because the Outlook Anywhere configuration in the Outlook client side will be updated by Autodiscover service every time
we open Outlook.
And we can run the following command: get-outlookanywhere | set-outlookanywhere -IISAuthenticationMethods  basic,Ntlm –
ClientAuthenticationMethod NTLM
Best regards,
Angela Shi
TechNet Community Support