By default, Edge Transport servers have anti-spam features enabled and Hub Transport servers have anti-spam features disabled. In an Exchange organization with Edge Transport servers, this is the desired configuration—you want your Edge Transport servers to run anti-spam filters on messages before they are routed into the Exchange organization. After Edge Transport servers have filtered messages, you don’t need to filter them again, which is why Hub Transport servers have anti-spam features disabled.
However, if your organization doesn’t use Edge Transport servers and has only Hub Transport servers, you should enable the anti-spam features on Hub Transport servers that receive messages from the Internet. You 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.
The following example shows how you can enable anti-spam features on a Hub Transport server named CorpSvr127: Set-TransportServer –Identity 'CorpSvr127' –AntispamAgentsEnabled $true
You then need to restart the Microsoft Exchange Transport service on the server. If you exit and restart the Exchange Management Console, you’ll then see the Antispam tab in the details pane. (Expand the Server Configuration node, and select the Hub Transport node.)
You can now configure the transport server’s anti-spam features.