moderated Re: Mail server reverse DNS still flakey #bug
Mail server lb01.groups.io is at 22.214.171.124 and lb02.groups.io is at 126.96.36.199 where both belong to Linode. (Links are to ARIN pages)
IP address 188.8.131.52 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.