I am using Parallels Plesk Panel 9.5.4 I am using one (1) IP address to host three (3) Domains. Everything is working fine except for the mail system. Whenever I check the settings thru mxtoolbox.com this error shows up 220 expertsonlive.com.ar ESMTP Postfix Reverse DNS FAILED! This is a problem. 0 seconds - Good on Connection time Not an open relay. 0.874 seconds - Good on Transaction time Session Transcript: HELO please-read-policy.mxtoolbox.com 250 expertsonlive.com.ar [140 ms] MAIL FROM: <email@example.com> 250 2.1.0 Ok [156 ms] RCPT TO: <firstname.lastname@example.org> 450 4.7.1 Client host rejected: cannot find your hostname, [18.104.22.168] [140 ms] QUIT 221 2.0.0 Bye [140 ms] What should I do? I have tried searching for answers for almost 12 hours to no avail. I still don't get the PTR fix. I tried removing the PTR and still to no avail.