LeadShield is Brandon Shelton's 3rd SaaS. He has a proven track record as far as the marketing and growth of his products go. His latest SaaS is a product that must exist, especially for marketers, helping you understand the people on your list, and determine if they're good leads or bad leads.

One thing I like about LeadShield is it's not an all or nothing system. Their tagging and analytics allow you to identify bad leads and not just block them, but understand how those email addresses are performing and decide what to do with them.