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List:       postfix-users
Subject:    Re: gmail reverse host issue
From:       lists <lists () lazygranch ! com>
Date:       2020-02-17 15:05:30
Message-ID: 28na0bnkcl8551l3koqs8t6u.1581951930023 () lazygranch ! com
[Download RAW message or body]

Thanks. I appreciate that postfix would kick out a different error. 




  Original Message  


From: wietse@porcupine.org
Sent: February 17, 2020 6:55 AM
To: postfix-users@postfix.org
Reply-to: postfix-users@postfix.org
Subject: Re: gmail reverse host issue


> Feb 17 06:18:10 mydomain postfix/smtpd[2619]: NOQUEUE: reject:
> RCPT from unknown[209.85.219.177]: 550 5.7.1 Client host rejected:
> cannot find your reverse hostname, [209.85.219.177];
> from=<some.person@gmail.com> to=<me@mydomain.com> proto=ESMTP
> helo=<mail-yb1-f177.google.com>

What you see IS NOT the result of Postfix timeout while it looks
up a hostname with the getnameinfo() system library routine.

Postfix will reply with 450 if the hostname could not be looked up
(which is different from a "DOES NOT EXIST" result), as shown in
the code fragment below. Postfix is very careful to avoid making
that mistake.

More likely your system library (see nsswitch.conf) makes the basic
mistake of confusing "lookup error" with "does not exist" (solution:
use a better OS), or less likely some DNS resolver is making that
mistake (solution: use a better DNS resolver).

Wietse

static int reject_unknown_reverse_name(SMTPD_STATE *state)
{
    const char *myname = "reject_unknown_reverse_name";

    if (msg_verbose)
        msg_info("%s: %s", myname, state->reverse_name);

    if (state->reverse_name_status != SMTPD_PEER_CODE_OK)
        return (smtpd_check_reject(state, MAIL_ERROR_POLICY,
                        state->reverse_name_status == SMTPD_PEER_CODE_PERM ?
                                   var_unk_client_code : 450, "4.7.1",
            "Client host rejected: cannot find your reverse hostname, [%s]",
                                   state->addr));
    return (SMTPD_CHECK_DUNNO);
}


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