Since a few days, we’re receiving SPAM with our own internal email addresses;
I guess the spammers are using an Exchange configuration which allow to send mail with internal users without authentication (MAIL FROM : firstname.lastname@example.org).
My question is quite simple: is there a way to prevent this ?
Do we got to configure that on the receive connectors properties ?
(We actually got 2: one on 25 port, another one on 465 port).