Open-source Superhuman alternatives

Mailspring is a desktop email client for Mac, Windows and Linux, built as a new version of Nylas Mail by one of its original authors. The interface is written in TypeScript with Electron and React, and the mail sync engine is written in C++ and runs locally on your computer. Both parts are open source under GPLv3.

Features include a unified inbox, snooze, send later, mail rules and templates, and a plugin architecture makes the app easy to extend. The README states that these features run in the client and that email credentials are not sent to the cloud. The IMAP-based sync engine replaces the earlier JavaScript sync code used by Nylas Mail.

A paid Mailspring Pro subscription unlocks extra features for people who send a lot of email, such as link tracking, read receipts, mailbox analytics and contact and company profiles. Compiled downloads are offered for Windows, macOS and Linux, including deb, rpm and snap packages.

Inbox Zero is an AI assistant for email, built to cut the time people spend in their inbox. It organizes messages, pre-drafts replies in the user's tone and style, manages the calendar and files attachments. It can also be chatted with from Slack or Telegram, and it is positioned as an open-source alternative to Fyxer that is more customizable and secure.

Its feature set includes AI rules written in plain English, Reply Zero to track emails awaiting a response, a bulk unsubscriber and bulk archiver, a cold email blocker, email analytics and meeting briefs that pull context from email and calendar. Smart filing saves attachments to Google Drive or OneDrive, and the project topics point to Gmail integration.

The app is built with Next.js, Tailwind CSS, shadcn/ui, Prisma and PostgreSQL in a Turborepo monorepo, with Upstash used for supporting services. A hosted version runs at getinboxzero.com, and the repository includes instructions for self-hosting. Feature requests go through GitHub issues or Discord, and the license is specified in the repository.

Zero is an open-source email application presented as a Gmail alternative that applies AI to the inbox. Its authors argue that most email services are closed source, data-hungry or too complex to host yourself, and they position Zero as transparent and privacy-first. It can be self-hosted while also connecting to external services such as Gmail and other email providers.

Listed strengths include a unified inbox that combines multiple providers such as Gmail and Outlook, AI agents and language models that help with email tasks, a customizable interface and an extensible design for developers. The project states that it does not track, collect or sell your data, while noting that data passed to connected external services falls under those services' own privacy terms.

The stack is Next.js, React, TypeScript, Tailwind CSS and shadcn UI on the front end, Node.js with Drizzle ORM on the back end, PostgreSQL for the database, and Better Auth with Google OAuth for sign-in. Running it locally requires recent Node.js, pnpm and Docker, plus environment variable configuration. The code is MIT licensed and the latest release listed is v0.1.