Attempt to relay mail messages appearing frequently

Greetings all!

I am seeing very frequently the following messages:

Attempt to relay mail from rubbish.com rejected for policy reasons. Relays from host denied in your configuration.

I am assuming that Domino is managing to block such relay attempts due to certain settings I have in my serve config document. In other words such messages are not being processed. How can I check that this is the case? And how can I stop such messages from appearing in my server console?

Thanks

Pierre