OK, I've opened a trouble ticket.
Yesterday, I got a message from spunkymail-a16.dreamhost.com saying that an email from one of my domains to an earthlink customer had bounced.
Earthlink had returned 500 on the smtp transaction with a message:
host mx1.earthlink.net[126.96.36.199] said: 550 550
Dynamic/zombied/spam IPs blocked. Write
email@example.com (in reply to MAIL FROM command)
OK, when I do a ping on spunkymail-a16. ... the returned IP address from the resolver is 10.3.39.113. That's a no-no! That IP address should never be exposed to the public internet. It is a reserved for private network space. If I were earthlink, I'd reject mail from there too.
I suppose that spunky... is just the host that is reporting the error to me. That the failing MTA is some other machine. The bad news, is that I cannot find the IP-address of the dreamhost machine that tried to pass off the message to earthlink so that I can look up the address in the public blocklists to see just how bad the problem is.
Does anyone else see this? Does anyone know what the outbound MTA's real IP-addresses are so I can look 'em up?