What is the best free tool to use to verify emails?
NeverBounce
This free email verifier is trusted by over 125,000 users, who enjoy its quick validation process and flexible pricing. You can pay as you go based on the number of addresses you validate, or you can pick a subscription plan for a volume discount.
How do companies verify emails?
At its most basic, email address verification is an automated process that uses rules and data to review your entire email address list and identify addresses that are either safe for sending, valid but risky or unknown, or invalid.