On 2023-02-27 at 04:49:55 UTC-0500 (Mon, 27 Feb 2023 10:49:55 +0100)
Fourhundred Thecat <[email protected]>
is rumored to have said:
On 2023-02-27 08:43, Matus UHLAR - fantomas wrote:
On 27.02.23 08:07, Fourhundred Thecat wrote:
The problem is, postfix does not seem to distinguish between IP
having
no DNS record, and my DNS server being temporarily unavailable.
why do you think that?
the error above is a "4xx" which means temporary error - the client
is
expected to retry.
are you sure about that?
That is how the reply code model for SMTP works: 4xx replies indicate a
transient error that is likely to resolve on its own, so the message
should be retried later.
If this wasn't honored, email would be unusably unreliable.
I am only seeing "450 4.7.25" regardless whether ip has no DNS record,
or whether DNS is temporarily unavailable.
That can be a local config issue. If Postfix gets a permanent DNS error
(i.e. NXDOMAIN or NOERR with zero answer records) it will send a 5xx
(i.e. permanent error) reply code. You can change that with
warn_if_reject.
When using the client hostname for validation, there are failure points
in reverse DNS and in resolving the client IP based on the PTR reply, so
if either part tempfails in DNS (SERVFAIL reply or timeout,) Postfix
will tempfail the message.
--
Bill Cole
[email protected] or [email protected]
(AKA @grumpybozo and many *@billmail.scconsult.com addresses)
Not Currently Available For Hire
