You can allow or reject a particular host's mail.

Allow mail from host

Deliver mail from host to local addresses:
When this option is selected, mail is delivered to local addresses but not to remote addresses.

Log recipient rejections to error log:
This option tracks which recipients reject mail from this host.

Send blind carbon copies (bcc) of all messages from this host to:
You can't select this checkbox until you click the Users & Groups button and drag the user or group (who will receive blind carbon copies) to the Mail From panel.

Copies of all messages from this host are sent to the user or group you specify.

Reject all mail from host

If you reject mail from a host, it is returned to the sender.

Log each rejection:
This option tracks rejected messages sent from the host.

Related topic

Mail host settings