If you're looking for a free, open-source tool to create calendar events from email threads while protecting your data privacy, fwd2cal is a great choice. It pulls relevant information from email threads you forward to it and creates calendar events in your Google Calendar. fwd2cal is designed with privacy in mind, with no storage of emails and logging only of email addresses. The tool also works with multiple email addresses and doesn't have a pricing plan yet, so it's free and private.
If you're more focused on scheduling meetings and generating leads, Meetz is worth a look. Meetz automates outreach, lead generation and meeting scheduling, and it's designed to comply with data privacy regulations like GDPR, CCPA and CPRA. It has a free plan with basic features, so it's accessible while still offering powerful tools to get your workflow in order.