Stack filters until the list is worth sending.

Every filter you add improves relevance and shrinks the pool, and there is a point where the list gets too small to learn anything from. As a rule of thumb, a few thousand well-matched records give you enough signal to read a response rate; a few hundred do not, unless the deal size justifies writing each message by hand.

Filter in the order that matters to your offer. Country usually comes first because it decides both language and legal footing. Then the attribute that most predicts need — industry for a vertical product, company size for a pricing-sensitive one, technology for anything that integrates. Seniority last, since it narrows hardest.

Because the price is flat, there is no reason to over-buy. Take the tight slice, mail it properly, and come back for the next one. That is the practical advantage of a one-time file over a credit-metered platform, where every extra filter tempts you to widen the net to justify the spend.