Proton

Proton is a secure collaboration platform offering encrypted email, calendar, and document storage.
Proton - Collaboration Productivity profile photo

System Parameter Breakdown

Free Plan:
Yes
Free Storage:
500 (MB)
End-to-End Encryption:
Yes
Max Users (Business Plan):
Unlimited
Calendar Sharing:
Yes

Proton provides end-to-end encrypted productivity tools including email, calendar, file storage, and document editing. It's designed for privacy-conscious professionals, businesses, and organizations that require secure communication and data protection without compromising on collaboration features.