moderated Re: Mail server reverse DNS still flakey #bug
Mail server lb01.groups.io is at 184.108.40.206 and lb02.groups.io is at 220.127.116.11 where both belong to Linode. (Links are to ARIN pages)
IP address 18.104.22.168 belongs to "PROOFPOINT-NET-NORTH-AMERICA" so that's not the correct address. Something else is wrong. Perhaps the issue is DNS at your provider or some kind of proxy.