Søren Schrøder wrote:
Greetings.
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Jun 30 07:55:42 mailgate postfix/smtpd[39222]: warning: \
87.53.72.254: address not listed for hostname mail.viauc.dk
Jun 30 07:55:42 mailgate postfix/smtpd[39222]: NOQUEUE: reject: RCPT from unknown[87.53.72.254]: 550 5.7.1 Client host rejected: cannot find your hostname, [87.53.72.254]; from=<REMOVED> to=<REMOVED> proto=ESMTP helo=<mail.viauc.dk> on the mailgate, I can resolve the "unknown" using my caching nameserver at 127.0.0.1 (using resolv.conf): # host mail.viauc.dk. mail.viauc.dk has address 87.53.72.234
^^^
# host 87.53.72.254
^^^
254.72.53.87.in-addr.arpa domain name pointer mail.viauc.dk.
Postfix resolves the IP first, and next resolves the name it got at step 1, and verifies the resulting IP is the same as the initial IP. The two does not match: 87.53.72.254 != ...234. It is exactly what it's talking about in the very first log line you quoted above. /mjt