What are some alternatives?
When comparing mails.wtf and Mail Dump, you can also consider the following products
Hunter - Find all the email addresses related to a domain
LeadGibbon - Access millions of business contacts, with verified email addresses and phone numbers
Find That Email - The yellow pages of emails.
Snovio - With Snovio you can find emails, verify them and run your email campaigns within minutes.
MailDump Verifier - Powerful Emails Verifying Tool that helps verify email address or validate email addresses
Norbert - Norbert is an online tool that helps you to find anyone’s corporate email address.