DuckDuckGo - The Internet privacy company that empowers you to seamlessly take control of your personal information online, without any tradeoffs.
Hunter - Find all the email addresses related to a domain
Google - Google Search, also referred to as Google Web Search or simply Google, is a web search engine developed by Google. It is the most used search engine on the World Wide Web
Snov.io - More leads. More sales. More revenue.
Searx - Open source metasearch engine
MailDump Verifier - Powerful Emails Verifying Tool that helps verify email address or validate email addresses