Outlook의 오픈소스 대체

End-to-end encrypted email with calendar and contacts — Tuta is an email service with a strong focus on security and privacy that lets you encrypt emails, contacts and calendar entries on all your devices.

↔ 대체: Gmail、Outlook、ProtonMail

Lightweight webmail that aggregates all accounts — Cypht: Lightweight Open Source webmail aggregator [PHP, JS]. Supports IMAP/SMTP, JMAP and EWS (Exchange Web Services)

↔ 대체: Outlook