Can bounces trigger throttling?

Bounces can trigger throttling:

How it happens:

ISP observes high bounce rate from sender. Treats this as suspicious behavior. Applies rate limits to further sends. Deferrals increase; delivery slows.

Throttling as protection:

Limits damage from potentially bad sender. Gives ISP time to evaluate. Forces sender to slow down and notice.

Bounce-to-throttling scenarios:

Spike in invalid addresses: Sudden list quality concern. New IP sending to old list: Spamtrap and bounce risk. Purchased list send: High bounces trigger defensive measures.

Breaking the cycle:

Clean list before resuming. Reduce volume. Improve quality metrics. Throttling may ease as metrics improve.

Throttling is the ISP saying "slow down and clean up." Bounces are part of the evidence prompting that response.