Short answer
HubSpot's KB: with bot filtering on, HubSpot excludes suspected bot activity from marketing email performance, including security scanners, privacy filters like Apple's Mail Privacy Protection, and corporate screeners such as Mimecast. Filtered numbers are usually lower than unfiltered ones. It's on by default, and each email's performance page shows whether it was on for that send.
1. Tracking settings
Bot filtering is part of HubSpot's analytics tracking settings. My demo portal's tracking settings:
2. Reading the numbers
- Judge engagement on clicks from real contacts and replies more than opens.
- See click rate vs click-through rate.