So there are tons of "email-sending" blacklists out there.

Are there "email-receiving" blacklists?  Is that a thing?

We're trying to get emails from Hilton Honors to our @tecnopolis.ca email
address(es) and they just refuse to send to us.  Even on the phone with
support to triple confirm the email address it refuses to send to us.

When I say refuses to send to us, I mean it won't even connect to port 25
on our server.  Just nothing, nada.  It's not a greylisting or RBL problem
on our side because it's not even opening a socket.  I can tell, I have
full access to the verbose mail logs and tcpdump.

All other vendors seem to have no trouble sending to us.  Just Hilton.
The big email providers like gmail send to us perfectly fine.  I've never
seen anything like this.

Now, I do have trouble sometimes with Akamai's *web* hit blacklist, though
I'm mostly "good" with them now.  People don't use Akamai *web* RBLs for
outgoing mail servers, do they?  Is that a thing?  I don't see that as an
Akamai product offering...
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