Gmelius - Gmelius is the first collaboration platform designed for G Suite and your company's daily tools.
HubSpot - Grow Better With HubSpot: Software that's powerful, not overpowering. Seamlessly connect your data, teams, and customers on one CRM platform that grows with your business.
Mailtrack.io - The best email tracking solution I've found. Free
MailChimp - MailChimp is the best way to design, send, and share email newsletters.
Followup.cc - FollowUp for email is a lightweight productivity suite that keeps your conversations and tasks from slipping through the cracks. Set perfectly timed reminders that arrive at the top of your inbox, right when you need them.
Marketo - Marketo's powerful marketing automation software helps marketers master the art & science of digital marketing to engage customers and prospects.