Email GitHub Repositories (2026) · Open Source Tools

Email for professionals and teams

Macro is a unified workspace for teams: email, chat, docs, tasks, agents, calls, and CRM — @-linked together with shared AI memory.

📧✨ Beautiful email. For everyone.

Monitors your RAM and reports any "quite terrible" unused capacity directly to the CEO of OpenAI.

Hylki (formerly Vireo): a fast, GNOME-native email client built with Rust and libadwaita.

💌 Build and send emails using React

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.

The largest open-source B2B cold outreach and email warmup service.

Self-hosted notification infrastructure for product notifications. One notify() call handles email, SMS, push, etc, with preferences, quiet hours, retries, fallback, scheduling, workflows, and delivery logs built in.

Prometheus Alertmanager

Self-hosted mail server for your own domain: SMTP/IMAP/POP3, CardDAV/CalDAV, React webmail and admin console, one-command Docker Compose.

Mail and calendar for Linux and macOS. Gmail and IMAP accounts, Google Calendar, contacts, OpenPGP and S/MIME. GTK4 and libadwaita, written in Rust.

Fully featured, open source, privacy friendly email app for Android

A self-hosted, unified webmail client.

The first Open-Source high-performance MTA developed from the ground-up for high-volume email sending environments.

Thunderbird for Android – Open Source Email App for Android (fka K-9 Mail)

Newsletters where you pay for the emails you send, not for dormant subscribers, at a fraction of the price of beehiiv and the like. Open source: self-host it, or use mailcheap.ai.

Built from the ground up for speed. Flectar Mail delivers native performance, instant startup, and about 20 MB of private memory at idle.

Keep passwords and other sensitive information out of your chat logs and inboxes.

:postbox: Gmail desktop app for macOS, Windows & Linux (formerly Gmail Desktop)