I don't have any inside info about all of Mailcore's spam filtering tech
stack, but many mail hosters will put their own domain name at the end
of hostnames they use for 3rd DNSBLs that they use, then restrict the
access to those dns servers (which are often specifically rbldnsd
servers), including doing this by answering "not listed" (NXDOMAIN) to
ALL unauthorized queries - which is an EASY-to-implement option with
rbldnsd - and so I think maybe they're doing that in this situation? -
if so, it's possible that this was never their own DNSBL. This MIGHT
even be Spamhaus' CBL list? (and if so, the IP is simply no longer
listed on CBL's list? ...but I can't confirm that this is the setup -
this is just a guess based on how they named this hostname
("cbl.mailcore.net"), and also based on many mail hosters implement
DNSBLs). So that's another possibility.
Rob McEwen, invaluement
------ Original Message ------
From "Peter N. M. Hansteen via mailop" <[email protected]>
To "Alessandro Vesely" <[email protected]>
Cc "mailop" <[email protected]>
Date 10/30/2025 6:54:53 AM
Subject Re: [mailop] Mailcore blacklisting
On Thu, Oct 30, 2025 at 11:21:56AM +0100, Alessandro Vesely via mailop wrote:
Hi,
I get:
554 5.7.1 Client host 94.198.96.74 blocked using cbl.mailcore.net
Their site doesn't seem to have any delisting functionality.
Has anyone ever been there and come out?
I don't think I had any interactions with them, but https://mailcore.net
ends up at a site that does have a "contact us" part.
And it looks like they could need a hand with certificates vs names.
All the best,
Peter
--
Peter N. M. Hansteen, member of the first RFC 1149 implementation team
https://nxdomain.no/~peter/blogpostshttps://nostarch.com/book-of-pf-4th-edition
"Remember to set the evil bit on all malicious network traffic"
delilah spamd[29949]: 85.152.224.147: disconnected after 42673 seconds.
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