CampaignKit - Email Validation for marketers. Detect invalid and malicious email addresses in your email lists.
NeverBounce - Real-time email verification and cleaning to ensure emails never bounce.
Null Bounce - Null Bounce is an email validation tool that helps companies decrease the bounce rate for email campaigns. Also, the service is available as an API, which can be used, for example, on sign-up forms to ensure that user submits a valid email address.
ZeroBounce - Removes invalid emails from your list to prevent email bounces from ruining your deliverability.
Captain Verify - Captain Verify is the best solution to Verify & Clean the validity of your emails.
Kickbox - Verify your email address lists with our drag and drop interface, or integrate into your app with our API. Prevent fake and bot account sign-ups by confirming your users are real humans with a real email address.