Maybe Exim should get a feature where you can define "protocol overrides" for domains, like so it
ignore specific protocol violations and such.
So if you have problem with a slightly misbehaving remote mail server, you can in a acl define how
exim should treat its responses (for example, treat it as temporary rejection, permanent rejection,
or just ignore it) - at different stages in the connection.
-----Ursprungligt meddelande-----
Från: Jeremy Harris via Exim-users <exim-users@???>
Skickat: den 3 september 2021 00:46
Till: exim-users@???
Ämne: Re: [exim] exim cant handle 521 response from remote MX
On 02/09/2021 20:25, krzf83--- via Exim-users wrote:
>>> Large email provider in my country uses 521 response at their MX for
>>> some kind of delaying. They don't care that its against rfc1846
>>>
>>> rfc1846 says:" A host which sends a 521 greeting message MUST NOT be
>>> listed as an MX record for any domain"
>>>
>>> # nc mx.poczta.onet.pl 25
>>> 220-mx.poczta.onet.pl ESMTP
>>> 521 5.7.1 Service unavailable; client [144.76.50.172] blocked using
>>> postscreenbl.opbl.onet.pl.local
That is not a consistent response. The first line is a 220 (with a flag
saying it will be a multi-line response). The second is a 521 (without
the flag, hence the last line).
All the lines of the response should have the same code
(RFC 5321 section 4.2.1 last para:
"In a multiline reply, the reply code on each of the lines MUST be the
same."
)
For what it's worth, testing from here gets a two-line response but
with 220 for both.
--
Cheers,
Jeremy
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