After I moved dns to CL, Postfix logs: Apr 21 09:55:33 sunucu postfix/smtpd: NOQUEUE: reject: RCPT from unknown[188.8.131.52]: 450 4.7.1 <externaldomian.here>: Helo command rejected: Host not found; from=<[email protected]> to=<[email protected]> proto=ESMTP helo=<externaldomian.here> But before holding dns records on ispconfig, there were no issue? I have deleted dns records and unchecked dns server in server config. I do not want to edit main.cf in postfix to allow reject_unknown_helo_hostname in postfix which may increase spam mails. Could this be because I was still holding dns records even I moved them to Cloudflare ? Should I wait?