What are some alternatives?
When comparing Email Hunter for Chrome and Hiver, you can also consider the following products
Hunter - Find all the email addresses related to a domain
Astro - The ASTRO Command Center software is specifically intended for use with: MixAmp Pro TR (late 2015 release), A50 Gen 3 with Base Stations (late 2016 release), A20 Wireless (late 2017 release).
Slik Prospector - Find anyone's email. No bounces.
MailClark - The Slack bot for external communications
Clearbit Connect - Clearbit Connect is a free extension that surfaces actionable information on the people who email you.
CleanEmail - CleanEmail is an online service that empowers you to take control of your mailbox.