All Time Warner Cable mail servers, whether inbound or outbound, will have DNS PTR records ending in 'mail.rr.com'.
Time Warner Cable has two classes of customers - Residential and Business Class. Residential customers are those who have Time Warner Cable service at their residence, while Business Class customers will typically have their service at their office or other place of business.
Many of our Business Class customers run their own mail servers, and we do not block outbound traffic to port 25 (the SMTP port) from either Residential or Business Class customer space at this time.
All Time Warner Cable Residential customers have dynamic IP addresses, and those IPs will all have PTR records ending in "res.rr.com", e.g., cpe-24-24-24-24.twcny.res.rr.com for IP address 18.104.22.168.
Time Warner Cable/Time Warner Cable Business Class customers may have either static or dynamic IP addresses; the default generic PTR record for this space will match the pattern "rrcs-AAA-BBB-CCC-DDD.foo.biz.rr.com", e.g., rrcs-208-125-77-3.nys.biz.rr.com for IP address 22.214.171.124. This default PTR record does not necessarily indicate a dynamic IP address; we make non-generic PTR records available to our Business Class customers that want to run their own mail servers, but not all take advantage of this service.
To aid those sites wishing to enforce a policy of not accepting inbound mail from dynamic IPs, Time Warner Cable regularly (at least once per week) provides a full list of our dynamic space to these public DNSBLs:
If you're a user of one of those lists, then you're already enforcing your policy on our dynamic address space; if you're not using any of those lists, and would like to get a regular feed of our dynamic IP space, please use the Contact Us links to begin that discussion with us.