I would like my sendmail to reject any emails presented that have a mismatched senders email@domain and host.domain. example: Return-Path: <info-c@xxxxxxxxxxxxx> Received: from global-change-mail.com (cug31-1-82-234-61-176.fbx.proxad.net [82.234.61.176]) I have been searching for a couple weeks off and on for the answer to this, but im having no luck at each attempt. Can someone shed light on how to force sendmail to demand that senders domain match the hosts domain? With rejection if they do not match? Reverse lookups are already enabled, but that seems to only see if the hosts reverse records exists, not whether or not the email being sent thru it is authorized. If this setting is even possible, yes, I realize the potential for false positives, but at this point, in my eyes, this is by far my best solution to rejecting spam on my private 5 account email server. Thanks in advance, jonathan