As I only have Hub Transport servers, I decided to enable the anti-spam features on Hub Transport servers that receive messages from the Internet.

We can enable or disable anti-spam features on Hub Transport servers using the Set-TransportServer cmdlet. To enable these features, set the -AntispamAgentsEnabled parameter to $true. To disable these features, set the -AntispamAgentsEnabled parameter to $false.

Here’s an example:
Set-TransportServer  –Identity ‘EXCH-SVR-NAME’  –AntispamAgentsEnabled $true

We then need to restart the Microsoft Exchange Transport service on the server.

If we exit and restart the Exchange Management Console, we’ll then see the Antispam tab in the details pane. (Expand the Server Configuration node, and select the Hub Transport node.)