What’s the risk of over-validation?

Over-validation removes legitimate addresses incorrectly identified as invalid. False positives in validation mean losing real subscribers. Aggressive validation can shrink lists excessively, removing engaged recipients.

Causes of false invalid results: catch-all domains reporting all addresses valid when some aren't real, temporary server issues causing validation failures, anti-spam measures blocking validation attempts, and aggressive risk scoring flagging legitimate addresses.

Balance validation by: understanding tool accuracy rates, testing against known-good addresses, implementing gradual suppression rather than immediate deletion, and preserving recently engaged addresses despite validation flags. Validation aids judgment; it shouldn't replace it entirely.