I have selected the option in WHM to verify a sender exists. For the most part, all mail is going out as it should and the system is doing what its supposed to be..except for 1 problem. All mail sent from root, specifically cpanel server notifications are not being delivered. I do get a bounce with the following message: This message was created automatically by mail delivery software. A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed: firstname.lastname@example.org SMTP error from remote mail server after RCPT TO:<email@example.com>: host mydomain.com [**.**.***.**]: 550-Verification failed for <firstname.lastname@example.org> 550-Previous (cached) callout verification failure 550 Sender verify failed ------ This is a copy of the message, including all the headers. ------ So, it seems that the issue only appears with mail sent by root. I haven't found a way to correct this and am looking for suggestions. For what its worth, I have multiple servers with the same set-up and those are working as they should. Its just this one particular server that it seems to be happening with.