[Exim] Auth

Helo list:

I have two servers one of them with Exim 3.33-1.1 and the other one with 3.12

I would like to don't permit that everybody can connect to my smtp port and make spam.

If i write in my exim.conf "relay_domains *" everybody can connect to my smtp port and make spam.

I have read the config.samples and i have set up as config.sample C039 but it don't work.

Please let me know how can i do for only can connect to my smtp port my users.

Best Regards.