A bounce report has a structure, even when it looks like a wall of text.

There is a human-readable part at the top, a machine-readable part with fields like `Status:` and `Diagnostic-Code:`, and often a copy of the original message headers. The format is defined in RFC 3464, which is why ESPs can parse bounces automatically.

If you have ever scrolled through one of these trying to find the actual reason, uChecker's page on Delivery Status Notifications shows where each piece lives and which field to trust.