Restricted inbound mail for users

Hello,

I need to setup for some users that they can’t sent and receive internet email. The only need internal mail.

Outgoing is no problem but for incoming i used this:

Deny messages intended for the following internet addresses:

I defined a notes group there but it’s only working when i put an email adres like me@example.com.

Is it possible to put Notes users in that group ?

Or is there a better way ?

Tnx