How do bounce spikes signal list quality issues?

Bounce spikes are diagnostic signals:

What spikes indicate:

Something changed in your list or sending. New addresses from untrusted source. Old segment being reactivated. List import without validation.

Common spike triggers:

New acquisition source: Purchased or scraped list. Dormant segment send: Old addresses gone bad. Database migration: Corrupted or outdated data. Suppression failure: Previously bounced addresses re-added.

Investigation approach:

Isolate which segment spiked. Identify data source. Check age of addresses. Review recent list changes.

Response:

Pause sending to problematic segment. Clean before resuming. Improve validation at source. Audit suppression processes.

Bounce spikes are the alarm bell. Something went wrong; investigate immediately.