Mailspring is a beautiful, fast, and fully open source email client for Mac, Windows, and Linux. Built on Electron and React with a C++ sync engine, it supports unified inbox, snooze, send later, mail rules, and templates with a powerful plugin system.
Scanned 6/8/2026
Install via CLI
openskills install agentskillexchange/skills---
name: "Mailspring Open Source Email Client with Plugin Architecture"
slug: "mailspring-open-source-email-client-plugin-architecture"
description: "Mailspring is a beautiful, fast, and fully open source email client for Mac, Windows, and Linux. Built on Electron and React with a C++ sync engine, it supports unified inbox, snooze, send later, mail rules, and templates with a powerful plugin system."
github_stars: 17366
verification: "security_reviewed"
source: "https://github.com/Foundry376/Mailspring"
category: "Calendar, Email & Productivity"
framework: "Custom Agents"
tool_ecosystem:
github_repo: "Foundry376/Mailspring"
github_stars: 17366
---
# Mailspring Open Source Email Client with Plugin Architecture
Mailspring is a beautiful, fast, and fully open source email client for Mac, Windows, and Linux. Built on Electron and React with a C++ sync engine, it supports unified inbox, snooze, send later, mail rules, and templates with a powerful plugin system.
## Installation
Use the upstream install or setup path that matches your environment:
- npm install
- npm start
- npm start -- --help
- npm run-script build
Basic usage or getting-started notes:
- profiles. **All of these features run in the client - Mailspring does not send
- To install all dependencies and run Mailspring from its source code,
- run the following commands from the root directory of the Mailspring repository:
- Source: https://github.com/Foundry376/Mailspring
- Extracted from upstream docs: https://raw.githubusercontent.com/Foundry376/Mailspring/HEAD/README.md
## Source
- [Agent Skill Exchange](https://agentskillexchange.com/skills/mailspring-open-source-email-client-plugin-architecture/)
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Ultra-compressed communication mode. Cuts token usage ~75% by speaking like caveman while keeping full technical accuracy. Supports intensity levels: lite, full (default), ultra, wenyan-lite, wenyan-full, wenyan-ultra. Use when user says "caveman mode", "talk like caveman", "use caveman", "less tokens", "be brief", or invokes /caveman. Also auto-triggers when token efficiency is requested.