Error Handling Patterns for Email Agents

Short summary

Email failures span synchronous codes (429 retryable, 400 and 403 are account states) and asynchronous bounces detected via webhooks. Agent Accounts track bounce and complaint rates silently until thresholds trigger review or sending suspension. Design resilience through address validation before sending, treating errors as states not transients, and consuming all deliverability webhooks for real-time visibility.

• •Synchronous send errors are categorical: retry only 429 (rate limit); halt on 400 (verification/pause state) and 403 (abuse block requiring support).
• •Asynchronous bounce webhooks reveal delayed failures; hard bounces (5xx codes) need suppression lists, soft bounces (4xx) allow capped retries.
• •Account-level metrics (bounce <2%, complaint <0.1% healthy thresholds) drive silent review phases before sending pauses; webhook telemetry is the only real-time visibility.

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