I defined a reverse DNS for the public IP of our SMTP


But still, the mail server of one of our customer answer

The mail system

: host mail2.domain.fr[xx.xx.xx.xx] refused to talk to me: 553 A reverse DNS record could not be found for

Final-Recipient: rfc822; user@domain.fr Original-Recipient: rfc822;user@domain.fr Action: failed Status: 4.0.0 Remote-MTA: dns; mail2.domain.fr Diagnostic-Code: smtp; 553 A reverse DNS record could not be found for

Why ?


Their mail server (or more likely another DNS server in between), has already looked up that IP and cached the response. Give it a day or two and the old response should eventually expire and look up the new record. Usually it happens much quicker than this, and usually a "no record found" response is not cached as readily as a "record found" response. But maybe in this case it is configured differently. Give it time and should start working soon. If it doesn't, then their DNS config is broken or for some reason cannot talk to the necessary DNS server to get your record.

  • My reverse dns record is older than a year, but you may have a point on badly dns server on the customer side... – Cédric Girard Dec 18 '16 at 11:20

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