Single verifier vs stacked verification

Single verifier vs stacked verification

Bad emails wreck bounce rates and reputation. How hard you scrub is a cost-vs-safety call.

Single verifier (ZeroBounce, NeverBounce) Pros:
— Cheap, ~$0.003-0.007/email
— Fast, one API call
— Catches obvious dead boxes

Single Cons:
— Catch-all and risky addresses slip through
— One engine's blind spots become yours

Stacked (verifier + MillionVerifier/Bouncer recheck) Pros:
— Catches what the first misses
— Pushes bounce under 2% on rough lists

Stacked Cons:
— Double cost and processing time
— Diminishing returns on clean lists

Verdict: Single 4/5 for fresh data, stacked 4.3/5 for scraped/aged lists.

Who it's for: One verifier is fine for Apollo/LinkedIn-sourced emails. Stack a second pass for scraped lists, anything over six months old, or new domains where you can't afford a reputation hit. Always test-send catch-alls in tiny batches rather than trusting any verifier's 'risky' label blindly.