[pfx] Re: I keep getting disabled on [email protected] mailing list

Just want to make sure this is what you think it is...

On Sun, 14 Jun 2026, Al via Postfix-users wrote:
>>>>>  [...]
>>>>>  I keep getting disabled on [email protected] mailing list. I
>>>>>  have resubscribed many times.

I presume you actually queried the list manager to verify your 
subscription or lack thereof...

>>>>> Is there a problem with my configuration?
>>>>>  What can I do to fix this?
>>>>
>>>>  You need to stop rejecting mail from the list. That could be because
>>>>  you've chose strict DMARC enforcement, which is incompatible with most
>>>>  discussion mailing lists.
>>>
>>>  I am not using DMARC.
>>
>>  That makes the situation less obvious.

;-)

>> Examine your logs to find the
>>  rejections, which should give you a hint as to why they are happening.
>
> I have taken a look at my logs:
>
> This is the error:
>
> Jun  9 12:03:41 sequoia postfix/smtpd[52759]: NOQUEUE: reject: RCPT from 
> unknown[45.90.5.195]: 554 5.7.1 Client host rejected: cannot find your 
> reverse hostname, [45.90.5.195]; from=<[email protected]> 
> to=<[email protected]> proto=ESMTP helo=<list.sys4.de>
>
> However, most of the of the time it lets, it through:
>
> 0.43, dsn=2.6.0, status=sent (250 2.6.0 <[email protected]> Message accepted 
> for delivery)
> Jun 14 06:35:36 sequoia postfix/qmgr[83260]: 4DC2D1F5A07: removed

45.90.5.195 is list.sys4.de:

     # dig -x 45.90.5.195 +short
     list.sys4.de.

It actually says this in the log message you posted:

     helo=<list.sys4.de>

>From this I skull that

     1) you are checking the reverse lookup and rejecting mail where the
        result doesn't match what was announced with HELO; and

     2) reverse lookups are failing

Where the reverse lookup is failing, I don't know.

This is probably a good time to ask: do you run a local caching DNS server 
alongside postfix (or within a couple of hops)? Aside from the Other 
Important Reasons, if you're not running it locally then you're not going 
to have logs to refer to; you might try tcpdump, but if it's a sporadic 
problem it might be a quiet day fishing.

--

Fred Morris, internet plumber

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