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.
UpLead is a B2B prospecting platform that provides B2B contact & company data. Features include real-time email verification, contacts in over 200 countries, 50+ search criteria, technology tracking, account based marketing, competitor intelligence, email pattern intelligence, social profile links, Salesforce & 12 other CRM integrations, and a robust API.
We like the intuitive user interface, and it's also nice how they flag contacts that are potentially not up-to-date, so you don't waste your credits!