AUP#I-1090 message issues - Time Warner Internet

This question is about "AUP#I-1090 message issues", with Time Warner Cable internet and apps. This really isn't so much a problem report as it is an attempt to document something that most (all?) of Spectrum tech support doesn't know about. My work servers just changed publicly facing IP addresses and those servers could no longer send mail to spectrum accounts (,,, etc). The message was:

refused to talk to me: 421 dnvrco-cmimta26 esmtp ESMTP server temporarily unavailable AUP#I-1090

I figured that AUP#I-1090 was an easy thing to look up but nobody knew what it meant. Turns out that this means that there are no reverse DNS records (PTR records in the domain) for the IP addresses I was sending from. I set some up and mail started flowing again. Note that the data portion of the RR doesn't need to point to an existing A or CNAME, my guess is just about anything will do but it does need to be there.

Hope this gets indexed by google and helps someone.

AUP#I-1090 message issues?