imapsync - Console-based utility for migrating IMAP mailboxes.
Hunter - Find all the email addresses related to a domain
MailStore - MailStore Home - A 100% free single-private-user desktop solution
Apollo.io - Apollo’s predictive prospecting, sales engagement, and actionable analytics help the teams to reach its full revenue potential.
audriga Email and Groupware migration - Easily migrate your email, contacts, calendar items and tasks to your new provider or server. No software installation is required.
Icypeas - This email finder has the capacity to bypass catch-alls