Currently I'm receiving just spam messages to abc@mydomain.com  (which the tech company "abc" keeps on trying to tell me isn't as a result of information leakage on their side).  I've just set up a legitimate account (that'll be ignored) of abc@mydomain.com as the only mail to that account is spam other than the legitimate emails where I've given said tech company another email address to send them to.  This will work until I run out of "free email accounts" to set up on the domain.  Is there a way I can blacklist a "TO Address" to block the emails?