FairValid is an email verification tool for sales and marketing teams. Check one address or an entire CSV list and get clear results: Valid, Invalid, Catch-all or Unknown. Credits are only used for Valid and Invalid results, so uncertain answers carry no net charge. You get 300 free credits every month, plus a REST API with scoped keys and sandbox testing, a website form widget, and integrations with Google Sheets, HubSpot and Mailchimp.