Towards the end of using self-hosted email at $dayjob, a couple of years ago now, Google started bouncing [some of] our email.

In the header for the bounce messages was included a description of the problem (as they perceived it), and a link for background reading.

I never followed up on it personally (that wasn't my job anymore because reasons), but the bounces seemed descriptive-enough for someone who was paid to care about it to make it work.

Was that not the case for you?