If you've recently tried to send an email and received an error message stating "The IP address sending this message does not have a PTR record setup," you're not alone. Based on our observations, we have noticed an increase in the number of interactions with Google returning this error message over the last few weeks.
While the number of emails affected by this error message is still relatively small in comparison to the total number of emails sent each day (26 out of 83,588 as of the time of this writing), we still consider it to be significant. As a result, we have taken steps to mitigate the issue by adding measures to our outbound relays, hopefully preventing any customers from seeing this error message moving forward.
It's important to note that we do not believe that the problem is related to any failure or bug in our own systems. Instead, we believe that it is currently a minor problem at Google. This means that, while we are taking steps to prevent the issue from affecting our customers, ultimately it is up to Google to address the underlying problem.