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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