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Month: February 2011 - DNS entry causing confirmation email to be rejected by postfix 'reject_unknown_client'

From: "David C. Rankin" <drankinatty@...>
Date: Mon, 28 Feb 2011 17:09:53 -0600

  I went to register for the bugzilla and found that the confirmation request
from was rejected by postfix because does not
provide a proper reverse lookup causing:

smtpd_client_restrictions = reject_rbl_client,

  It is 'reject_unknown_client' causing the rejection. From: the rejection is caused when:

1) the client IP address->name mapping fails, 2) the name->address mapping
fails, or 3) the name->address mapping does not match the client IP address.

  I'm no postfix expert, but to let the confirmation through, I just removed
'reject_unknown_client'. If there have been people who don't get the
confirmation emails, this may one reason why :)

  The actual postfix rejection was:

Feb 28 16:22:21 nirvana postfix/smtpd[6858]: warning: address not
listed for hostname
Feb 28 16:22:21 nirvana postfix/smtpd[6858]: connect from unknown[]
Feb 28 16:22:22 nirvana postfix/smtpd[6858]: NOQUEUE: reject: RCPT from
unknown[]: 450 4.7.1 Client host rejected: cannot find your
hostname, []; from=<bugs@...> to=<snip>
proto=ESMTP helo=<>
Feb 28 16:22:22 nirvana postfix/smtpd[6858]: disconnect from unknown[]

  Somebody smart with postfix and bind can probably tell you what the exact
issue is. Just looking, I see a helo from and the "warning: address not listed for hostname"

David C. Rankin, J.D.,P.E.