Charter/Roadrunner bounces?

I'm pulling together information from various sources here, and using a bit of guess work. So keep in mind that this info is not guaranteed.

When sending mail to Charter/TWC/RoadRunner domains (full list here), are you seeing any of these bounces?

• 550 5.1.0 sender rejected AUP#I-1310
• 550 5.1.0 sender rejected AUP#I-1320
• 550 5.1.0 sender rejected AUP#I-1330

These apparently correlate to the ISP's Cloudmark servers putting a sender into a rate limited "time-out" for anywhere from five minutes up to 24 hours. According to a post on Mailop from 2017, one bounce means 5 minutes, another means a one hour timeout, and the third means a 24 hour timeout. They might be listed in that order above, but I'm not sure.

Anyway, the net here is: In addition to investigating the underlying potential reputation issue (don't be a spammer, please?), you might want to slow down sending if getting the first or second error message. Perhaps throttle sending to trickle out over a number of hours instead of allowing as much mail to send as possible at any given second.

Information on dealing with Charter/Roadrunner deliverability issues is sparse (they no longer have a Postmaster site, alas), so I thought it'd be good to share this (best guess) information here with the hope that other folks will find it useful.