Block EWS In Exchange

You cant really do that unless you perhaps set allowd IPs on the EWS virtual directory or use a load balancer / reverse proxy that allows you to target the EWS directory.

Note that

https://video2.skills-academy.com/en-us/exchange/architecture/client-access/load-balancing?view=exchserver-2019

You can use this as a guide and set on the EWS virtual directory instead:https://blog.expta.com/2018/10/how-to-block-external-access-to.html

@Nandan NK

To block external access to Exchange Web Services (EWS) in Exchange Server 2019, you can use the Set-OrganizationConfig cmdlet in the Exchange Management Shell. Here are the steps:

1. Open the Exchange Management Shell.
2. Run the following command: Set-OrganizationConfig -EwsAllowList @{Add="InternalIPorFQDN"} -EwsBlockList @{Add="*"} Replace "InternalIPorFQDN" with the IP address or fully qualified domain name (FQDN) of your internal Exchange server. This will allow only internal users to access EWS and block all external access.

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