Return Path Certified

From Wttw

The Return Path Certified whitelist (formerly known as the SenderScore Certified, and before that, Bonded Sender) is an IP-based whitelistlist maintained by Return Path. Return Path recommends that ISPs accept mail from and give preferential delivery treatment for IPs on its Certified list. The Return Path Certified list currently covers 1.8 billion email inboxes, receiving preferential inbox treatment at dozens of ISPs.