RocketReach provides real-time verified data for 450 million professionals across 17 million companies, worldwide.
RocketReach is very user friendly, and generally their data is high quality. We like that it marks personal emails so you can assess whether it is appropriate to contact that person there.
ZoomInfo is a growth acceleration platform delivering accurate and actionable contact and business information to empower your sales, marketing, and recruiting teams.
This one's for the big boys. It's not cheap, but Zoominfo is one of the market leaders when it comes to enterprise data needs.