No idea where else to ask this and get a real qualified answer but here. Not exactly pure centos question....but... I am adding blacklists to my postfix smtpd settings. I have the inkling that after the first lookup for a domain or ip that my dns caches the result and I no longer bother the RBL or RHSBL list owners anymore in that instance. Is that correct? I hate to waste their resources if it is not. thanks, bob