LibreMailCal

An open-source, privacy-respecting, cross-platform email, calendar, contacts, and chat client built with Flutter.

LibreMailCal brings email, calendars, contacts, Matrix chat, and ERPNext notifications together in a single application across every major platform, while fully respecting your privacy. Your data stays on your device and the servers you choose: no tracking, no data harvesting, and no training of AI on your data.

Why It Exists

As of early 2026 there is no single open-source application that provides email, CalDAV (calendar), and CardDAV (contacts) across all major platforms (Linux, macOS, Windows, Android, iOS, and Web). Existing options each cover only part of the need:

  • Thunderbird Desktop covers email, calendar, and contacts, but its macOS support is inconsistent.
  • Thunderbird for Android (formerly K-9 Mail) is email only, with no CalDAV or CardDAV.
  • Thunderbird for iOS is in early alpha, email only.
  • DAVx5 is an excellent CalDAV/CardDAV adapter, but Android only.
  • Apple Mail, Outlook, and Gmail clients support these protocols but are proprietary and increasingly harvest your email and calendar content.

LibreMailCal exists to fill that gap: one unified, open-source application that handles email, calendars, contacts, and more across every platform, with privacy as the default.

What It Does

  • Email — IMAP/SMTP with IMAP IDLE push, across unlimited accounts, with an optional combined inbox view.
  • Calendar — CalDAV plus ICS subscriptions, full read/write sync with offline support, across multiple calendars with an optional combined view.
  • Contacts — CardDAV, full read/write sync with offline support.
  • Chat — a Matrix client supporting multiple Matrix-Synapse homeservers, with an optional combined view.
  • ERPNext notifications — receive and view alerts from multiple ERPNext servers, with more modules (project management, HR, CRM) planned.
  • Multi-account everywhere — unlimited email, calendar, contacts, and chat accounts, each with optional unified views.
  • Cross-device sync — optional, user-controlled configuration sync across your installations, carried over a private end-to-end-encrypted Matrix-protocol channel on a server you choose.
  • Offline-first — full functionality without network connectivity; sync happens in the background when you are online.
  • Privacy by design — encrypted data, no telemetry, no analytics, no third-party tracking, and no AI training on your data.

Platforms

LibreMailCal is built from a single Flutter codebase. Current build status:

  • Android — in Google Play review.
  • iOS — verified on iPhone (also available as an iOS PWA).
  • Linux — .deb package available (Debian 12+).
  • macOS — verified on MacBook Pro.
  • Windows — build in progress.
  • Web — self-hosted PWA, in progress.

How It Is Built

  • Protocol-native — direct implementation of IMAP, SMTP, CalDAV, CardDAV, and WebDAV, with no proprietary intermediaries.
  • Offline-first — all data syncs to a local, encrypted database so the app works without connectivity.
  • OOAD-oriented — object-oriented design throughout, with a clear separation of UI, business logic, and data access for maintainability.
  • Privacy by design — no telemetry, analytics, or third-party crash reporting; your data stays on your device and your chosen servers.

Status

LibreMailCal is in active pre-alpha development. Email, CalDAV, CardDAV, Matrix chat, and ERPNext alerts are functional; account export/import and cross-device account sync are complete. This is early-stage R&D, not production-ready. Sanitized public open-source releases are being prepared.

Where to Get It

Public open-source releases are being prepared. LibreMailCal is authored by Hawke Robinson and hosted by Dev 2 Dev Portal LLC. More at www.hawkerobinson.com.