Through HubSpot Sales for Windows you can receive real time notifications to know when a lead opens or clicks and email, you have been assigned a task, and more.
Install the HubSpot Sales for Windows add in
Before installing the Windows add in, make sure you've downloaded the Outlook or Office 365 add in to enable sending tracked and logged emails.
Download the Sales for Windows installer
NOTE: In addition to real-time notifications, you can view all notifications in your activity feed by clicking the HubSpot icon in your Windows menu]