MX servers refusing mail from host via ipv6

Paul van der Zwan paulz42 at
Fri Oct 1 12:37:11 UTC 2021

It looks like the <> servers are refusing mails from unresolvable hosts:

2021-10-01T11:49:53.891959+02:00 <> MyMailRelay sm-mta[78439] 1918bDet078021: to=<freebsd-questions at <mailto:freebsd-questions at>>, ctladdr=<XXXXXX at <mailto:XXXXXX at>> (544/544), delay=01:12:35, xdelay=00:00:03, mailer=esmtp, pri=336150, <>. [IPv6:2610:1c1:1:606c:0:0:19:5], dsn=4.7.25, reply=450-4.7.25 Client host rejected: cannot find your hostname, [2001:1af8:4700:a116:1::42], stat=Deferred: 450-4.7.25 Client host rejected: cannot find your hostname, [2001:1af8:4700:a116:1::42]

For IPv6 this seems like a very strict requirement as it’s almost impossible to get reverse DNS working for autoconfigured IPv6 adresses ?

Is there an IPv4 only alias I can route mail to for <> domain ?


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