How do Gmail, Yahoo, and Outlook label bounces differently?

Major providers have distinct bounce labeling styles:

Gmail approach:

Verbose, human-readable text. Multi-line responses. Specific policy explanations. Links to support documentation. Example: "Our system has detected that this message is likely spam."

Yahoo approach:

"Deferred" messaging for throttling. Policy references without details. TS-series codes for throttling. Example: "421 4.7.0 [TS01] Messages deferred due to policy."

Outlook/Microsoft approach:

Alphanumeric codes (RP-001). Structured enhanced codes. More terse messages. Example: "550 5.7.606 Access denied, banned sending IP."

Implications:

Gmail: Rich information, easy to understand. Yahoo: Requires interpretation, less detail. Outlook: Structured, requires code lookup.

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