Hunter - Find all the email addresses related to a domain
Spamihilator - The free Anti-Spam-Filter Spamihilator removes more than 98% of spam mails before they even get into your inbox.
Snov.io - More leads. More sales. More revenue.
SpamAssassin - Use this program to "Unspam" your mailbox(es).
MailDump Verifier - Powerful Emails Verifying Tool that helps verify email address or validate email addresses
Spam Reader - Spam Reader is a free anti-spam add-on for Microsoft Outlook.