term
Soft bounce
A temporary delivery failure.
A soft bounce means delivery failed for a temporary reason such as a full mailbox, greylisting, rate limiting, or a transient server issue. Providers usually retry soft bounces before converting them into final failures.
reading this as teams choosing a transactional API
Judged purely as an API. What the request contract guarantees on retry, how complete the webhook event coverage is, whether suppressions are readable and writable programmatically, and how much the message log retains when something needs debugging in production.
Applied to soft bounce, that means weighing idempotency keys, webhook coverage, event stream, and operating track record ahead of the rest, against high-frequency programmatic sends where a missed delivery is a product failure.