Hi Jayson,
Roadrunner has been problematic in this way for decades. They don't explain, they don't provide policy information or contact addresses, and their staff have frequently been snotty about DoS'ing their own customers.
You may have already seen this thread on the Spectrum forums. I think that help requests from RR users will be most likely to get them to take action. This suggests that there are channels available to customers (apparently not very well publicized to RR users either!)
https://forums.timewarnercable.com/t5/Email/Listserve-messages-sent-to-my-Ro...
----- Transcript of session follows ----- ... while talking to dnvrco-cmedge01.email.rr.com.: <<< 554 dnvrco-cmimta17 esmtp ESMTP server not available AUP#I-1000
Various attempts at Googling this error have lead me to believe that my IP may have been blacklisted by RR/TWC for some reason.
Seems logical. 554 is an administrative denial, not a server issue, and AUP is likely to abbreviate "Acceptable Use Policy". As you say, if you don't get to HELO it's an IP-based or reverse-DNS-based policy of some kind.
Does anyone here know of an up-to-date link where I can find out if my IP is blacklisted by them, submit a removal request, etc?
The only thing I can suggest is mail to postmaster. (I seem to recall that that address may have been non-functional at times, and it's mentioned in the thread....)
Steve