Open Source Apps with 'Unified inbox' feature

Cross-platform email client providing POP/IMAP support, robust filtering, multiple accounts, and chat. Extendable via add-ons with RSS/Atom, etc.

Secure Swiss-based email with end-to-end encryption and zero third-party access. Available across devices, offering a free version to promote privacy.

K-9 is an open source email client for Android with multi-folder sync, email signatures, Bcc-to-self, return-address configuration, keyboard shortcuts, Exchange Support, message flagging, IMAP deletes, saving attachments, configurable notifications and more.

Open-source client enhancing Thunderbird with more features and bug fixes. Offers security patches and multi-row descriptions like Outlook.

Unifies chats from 14 messaging networks in a single inbox, ensures privacy with on-device connections, and offers reminders, scheduling, and sync across devices.

Uses email as a decentralized chat platform with modern interface, open source code, no central servers, strong privacy controls, and no account signup.

Privacy-focused, open-source email app offering encryption, unlimited accounts, customizable features, unified inbox, and low data usage.

Boost your productivity and send better email with Mailspring, a beautiful, fast email client for Mac, Windows, and Linux. Mailspring is free to use and an optional pro version adds read receipts, send later, reminders and more.

ERPNext is a free and open-source integrated Enterprise Resource Planning (ERP) software developed by Frappé Technologies Pvt. Ltd. and is built on MariaDB database system using a Python based server-side framework.

Anbox puts Android into a container and every Android application will be integrated with your operating system. Any Android version is suitable for this approach and try to keep up with the latest version from the Android Open Source Project.

Wino is a lightweight native mail client for Windows 10/11. It is still in active development. Main motivation for this project is to replace Mail & Calendar for Windows with modern Windows design without using web technologies for speed.

Open source alternative to Intercom, Zendesk, Drift.com, Crisp, etc.

NexMail is an open-source, modern webmail client designed for self-hosted email servers. Enjoy a clean, intuitive interface with powerful features for managing your emails efficiently.

Open-source email client with unified inbox, IMAP/SMTP, OAuth2 support, conversation threading, TipTap rich text composer, contact sync, dark mode, and keyboard shortcuts.

Open-source, all-in-one productivity platform. Email, calendar, chat (AI), messages, files, projects, and dashboard — in a single app.

Spot-On is Encryption software that securely connects two friends for chat, group chat, email, file sharing and file transfers with magnet links and P2P web search.

Aster is a privacy-focused, quantum-safe, end-to-end encrypted email service. Unlike other encrypted email providers, Aster uses standard OpenPGP (RSA-4096) with portable keys that work in GPG, Thunderbird, or any other PGP client.

Smoke Messenger is an open-source Instant Messenger that is known as the first mobile Messenger worlwide using the encryption algorithm McEliece. To be downloaded at F-Droid.org or Github.com. Smoke provides with its own Server-Software: SmokeStack-Echo-Server.

Transform chaotic inboxes into organized workflows. See all your email folders as kanban columns. Combine all your Gmail, Outlook and more accounts into one unified view.

All of your private messages (Email, Facebook, Twitter, Instagram etc.) through a single login.

ERC, an acronym for "Emacs IRC," is a feature-rich IRC (Internet Relay Chat) client integrated into the GNU Emacs text editor. It provides users with a convenient and powerful tool for connecting to and participating in online chat networks.

A beautiful and functional email client for your terminal, built with Go and the charming Bubble Tea TUI library. Never leave your command line to check your inbox or send an email again!.

Kurrier is a modern, self-hosted workspace for email, calendar, contacts and storage.