Cox

Cox provides high speed network access as well as mailboxes for their subscribers.

Delivering to
Cox throttles mail based on sender reputation, both IP based and domain based. Senders are limited to opening 5 connections per IP address. They also have a published limit of 100 messages per connection.

Some business domains are hosted by Cox, but do not offer general hosting. Email addresses in the cox.net domain belong to subscribers, addresses in the cox.com domain are reserved for Cox employees. This page discusses filtering and limits on the cox.net email addresses.

Postmaster pages
Cox has an extensive set of postmaster pages providing information about delivering mail to cox.net email addresses.

Feedback loop
There is a feedback loop for cox.net email addresses. The FBL is administered by Return Path. Applications are accepted at the Cox FBL signup page. IP addresses will only be accepted if their SenderScore is above 60 or if their SenderScore is between 30 and 60 and the IP does not appear on any DNSBLs. IP addresses with a SenderScore below 30 will not be accepted.

Whitelist
Cox does not offer whitelisting services.

Certification Services
Goodmail reports that Cox is a Goodmail partner.

Cox also uses the Return Path Certified whitelist in mail delivery decisions. Mail from IPs on the Return Path Certified list will see better delivery at Cox domains.

Support for Senders
As part of their postmaster webpages, they maintain a comprehensive list of error codes returned in response to blocked email. They also provide a blocklist removal form. Cox does not provide any formal way to contact them directly.

Known spamfilters
Cox uses a number of commercial spam filters and spamfiltering services. These include the Spamhaus ZEN, Invaluement ivmSIP DNSBL , Invaluement ivmURI , Return Path Reputation Network Blacklist , SURBL , URIBL.