I have an internal email server that is hosted locally using a public ip from my isp. i have noticed that i can sen email to yahoo but email send to gmail and others are not been received. emails sent from my server are been received on yahoo mail servers. however emails cannot be sent yahoo to my private email servers. i looked at logs of the delivery failure notification and i have seen that ” google do not accept emails from by my ip 126.96.36.199 because it does not have a PTR record or a reversed lookup for my domain mydomain.com.