A client was moved from a on-premise Exchange environment over to a hosted cloud service and some senders are getting NDR messages stating their AAAA record isnt correct.
This is the message:
#< #5.4.4 X-Postfix; Host or domain name not found. Name service error for name=mail.oldemailserver.com type=AAAA: Host not found> #SMTP#
Their current setup allows email to flow to a cloud spam filter service then shoots over into the hosted mail platform via smarthost.
I have yet to hear back from my cloud filter service but I'm thinking they're not ready for an IPv6 RR.
I'm just thinking that the email source records need to be updated (dns flush). Would someone confirm this hypothesis or point me in the right direction please?