Propeller CRM - Small business CRM with deep Gmail integration

GetNotify - GetNotify is a free email tracking software solution.

Cloze - Smarter Relationship Management

Bananatag - Find out what happens to your emails after you press send! Add email tracking, attachment tracking, email scheduling and templates to your daily emails.

Highrise - Save and organize notes and email conversations for up to 30,000 customers and contacts. Keep track of proposals and deals.

Intelliverse Email Tracker - Intelliverse Email Tracker provides insights to increase the ​productivity of your emails.