On 2024-10-21 at 16:43:05 UTC-0400 (Mon, 21 Oct 2024 16:43:05 -0400)
Steve Matzura via Postfix-users <s...@noisynotes.com>
is rumored to have said:

[ big snip...]

Here's a returned mail message I received when I tried to simply send a message to myself. This shows me no mail is going out at all. I actually was

[...]

<s...@noisynotes.com>: host mail.gandi.net[217.70.178.9] said: 554 5.7.1
    <unknown[92.243.26.209]>: Client host rejected: Access denied (in reply to
    RCPT TO command)

This is how the DNS for your mail server looks from here:

        # host 92.243.26.209
        209.26.243.92.in-addr.arpa domain name pointer xvm-26-209.sd6.ghst.net.
        # host xvm-26-209.sd6.ghst.net.
        Host xvm-26-209.sd6.ghst.net. not found: 3(NXDOMAIN)

This is a typical pattern for compromised hosts which send spam and other bad traffic. The PTR returns a name which is clearly derived from the IP and which does not itself resolve. Very sketchy. As this appears to be a Gandi IP address and you're talking to a Gandi machine, which is giving you a policy prohibition (5.7.1) error code. Talk to Gandi. If you're sending mail, even through a smarthost, you should have a REAL name, not something invented by your host.

I suspect that you or they must fix your DNS so that both your IPv4 and IPv6 addresses have "reverse DNS" (PTR records) resolving to a name which has forward (A and AAAA) DNS records resolving that name back to the same network addresses.

You should also use that name as your smtp_helo_name, which by default is set equal to $myhostname.

It is not possible to say for sure what changed to make this happen, as it could be entirely internal to Gandi.


--
Bill Cole
b...@scconsult.com or billc...@apache.org
(AKA @grumpybozo@toad.social and many *@billmail.scconsult.com addresses)
Not Currently Available For Hire
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