Apollo.io

Apollo.io is a B2B lead intelligence and sales engagement platform combining a database of 275 million professional contacts and 73 million companies with built-in email sequencing, LinkedIn integration, and AI-powered personalization. Founded in 2015, Apollo has become the most widely used sales prospecting tool for SDR and outbound sales teams in the SMB and mid-market segment. Apollo's core value is its contact data quality — verified business email addresses, direct phone numbers, LinkedIn profiles, and firmographic data (company size, industry, technology stack) for millions of professionals. Unlike ZoomInfo (which licenses data to organizations), Apollo provides per-seat access to the full database at a dramatically lower price point, making it accessible to early-stage startups. Apollo Sequences enables outbound email and LinkedIn touch campaigns with multi-step branching logic, A/B testing, automatic bounce handling, and reply detection. Apollo's AI personalization (Apollo AI) generates customized email openers based on the prospect's LinkedIn profile, recent company news, and firmographic signals.