Cannot send email: The IP address sending this message does not have a 550-5.7.25 PTR record setup

[josephgodwinke]

Hello @maxwell

@maxwell

The IP address sending this message does not
    have a 550-5.7.25 PTR record setup, or the corresponding forward DNS entry
    does not 550-5.7.25 point to the sending IP. As a policy, Gmail does not
    accept messages 550-5.7.25 from IPs with missing PTR records. 

Add a PTR record where you purchased the server - mail.primarydomain.com see this How to set rDNS in Cyberpanel - #2 by josephgodwinke