SMTP error from remote mail server after end of data:

    host gmail-smtp-in.l.google.com [64.233.161.27]:
    550-5.7.1 [xx.xxx.xxx.xxx] The IP address sending this message does not have a
    550-5.7.1 PTR record setup. As a policy, Gmail does not accept messages from
    550-5.7.1 IPs with missing PTR records. Please visit
    550-5.7.1  https://support.google.com/mail/answer/81126#authentication for more

550 5.7.1 information. d129si35572832lfg.31 - gsmtp