On Tue, 12 Jul 2005, Jakob Hirsch wrote:
> Reinhard Haller wrote:
>
> > A typical example is the sender-address
> > c_sshaw@???
> >
> > There is no MX record and no A record for the
> > domain (servfail). Exim issues a 451 response which
> > doesn't really help in this case.
>
> Hm?
>
> mail from:<c_sshaw@???>
> 550-Verification failed for <c_sshaw@???>
> 550-Unrouteable address
> 550 Sender verify failed
That's somewhat churlish. I've frequently encountered situations
which give SERVFAIL one day (with a 4xx response) and Unrouteable
(with a 5xx response) on another day.
Anyway, as seen from here:
Can't find MX records for smartlife.co.uk: SERVFAIL
My response involves a file (or .db if you prefer) listing domains
which we believe to be unreachable, or not participating properly in
email, for various reasons (such as SERVFAIL, protocol-violating
responses, postmaster rejection, abuse mailbox full, and so on).
There's relatively few domains in there, don't get me wrong, and most
of them are abusive for other reasons too. This file is checked
before trying the DNS, and if the domain is in the list, we tell them
the good news:
message = We are currently unable to accept mail from \
$sender_address_domain \
because that mail domain is persistently unreachable or not \
responding properly, for reasons outside our control.
That way, they get an immediate (permanent) rejection from us, instead
of retrying for days on end with tempfails. Of course we also need a
little script to do housekeeping on the list, in case things have got
better since we listed them.
I'm not aware of anything in exim itself that could turn this tempfail
into a permfail - and, indeed, doing that for something involving the
DNS seems rather risky to me, since occasional DNS glitches are by no
means unusual.
best regards
