MailTracker - MailTracker is a mobile email tracking solution.
NinjaOne - NinjaOne (Formerly NinjaRMM) provides remote monitoring and management software that combines powerful functionality with a fast, modern UI. Easily remediate IT issues, automate common tasks, and support end-users with powerful IT management tools.
Mailtrack.io - The best email tracking solution I've found. Free
Atera - Atera’s all-in-one platform enables IT professionals to gain access, visibility, and control over all their networks and devices from anywhere, so they can work smarter and light years faster.
Hunter - Find all the email addresses related to a domain
Microsoft Operations Management Suite - Microsoft Operations Management Suite enables user to gain visibility and control across the hybrid cloud with simplified operations management and security