Hunter - Find all the email addresses related to a domain
Bulk Email Verifier - Clean up your large mailing lists before you use them. Clean list increases your reputation in MailChimp, AWeber, or Campayn.
MailDump Verifier - Powerful Emails Verifying Tool that helps verify email address or validate email addresses
Email Verifier - Email verifier app lets you verify email.
Mail Dump - Powerful Extensions for email addresses extracting, verifying and finding
Email List Verify - The Fastest Way to Improve Email List Deliverability and ROI