Quality, and the reason people underweight it comes down to deliverability, not just conversion. Sending 100 unverified addresses a day means bounces and the odd spam trap, and those signals tell mailbox providers your sending is careless. That reputation hit follows every message after, so even your good, well targeted emails start landing in spam or getting throttled. Unverified volume doesn't just waste the bad addresses, it quietly taxes the whole program.
Ten verified, relevant contacts beat a hundred unverified ones because replies come from two things stacked together: real fit and a clean sending reputation. Volume only starts paying off once both are locked in, and on a dirty list it just amplifies the damage.
So the order that works: verify first to kill bounces, segment tight so every send fits the person, then scale volume inside that clean list with warmed sending and sane pacing. Quality gates quantity, not the reverse. And measure replies per hundred sent per segment, not raw send count, or you're flying blind.
Best,
Floqal