Check if you've enabled Pipedrive - Calendar integration
If so, since you also have Pipedrive-Klenty integration, all your email engagements from Klenty, is syncing back to Pipedrive, which in turn syncs to your calendar.
Open Pipedrive and head over to your Profile icon > Company Settings > Personal > Calendar Sync > Uncheck all the Klenty engagement tags and E-Mail checkbox present in the Calendar sync section.
Doing so, the Klenty activities will not sync with your calendar.
