Remote host said: 550-5.7.25 [203.152.198.135] 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 match the sending IP. As a policy, Gmail does not accept messages
550-5.7.25 from IPs with missing PTR records. For more information, go to
550-5.7.25
https://support.google.com/a?p=sender-guidelines-ip
550-5.7.25 To learn more about Gmail requirements for bulk senders, visit
550 5.7.25
https://support.google.com/a?p=sender-guidelines. 41be03b00d2f7-7db4999d472si7073148a12.602 - gsmtp
このようなエラーになっております。PTRレコードとマッチしていないために起きているようです。