jrs235 is referring to IP reputation as measured on the receiving end of the email. In other words, Yahoo or Hotmail might reject your emails if they see unusua

jrs235 is referring to IP reputation as measured on the receiving end of the email. In other words, Yahoo or Hotmail might reject your emails if they see unusual activity from an IP address. Until an IP is "established" as having sent a lot of email with low bounce and spam rates, getting bulk email delivered from that IP address will be a frustrating experience.