K-9 Mail

If you want a powerful, privacy-respecting email app that gives you full control, K-9 Mail is one of the most trusted open-source email clients for Android. Designed for speed, stability, and customization, it supports IMAP, POP3, and SMTP, allowing you to use almost any email provider — from personal accounts to custom domains.

K-9 Mail offers a clean and efficient interface without ads, tracking, or hidden analytics. You get advanced features like unified inbox, message threading, encryption support, multi-account management, and rich customization options. Whether you're a professional user with multiple accounts or simply want a lightweight alternative to bloated email apps, K-9 Mail delivers a smooth and dependable experience.

As part of the Thunderbird project, K-9 Mail continues to evolve with modern interface updates and improved security features, while keeping the transparency and freedom of open-source software.

Key Features

• Supports IMAP, POP3 & SMTP for all major email providers
• Multiple accounts with unified inbox
• OpenPGP encryption via OpenKeychain
• Clean, lightweight, and intuitive interface
• Advanced email organization with folders, filters & search
• Configurable notifications per account or folder
• Sync settings, background fetch, and message threading
• Customizable swipe actions, themes, and appearance
• No ads, no tracking, no proprietary dependencies
• Fully open-source with active development

Why Users Love K-9 Mail

• One of the most trusted open-source email apps on Android
• Complete control over privacy and email behavior
• Highly customizable for both casual and power users
• Works with self-hosted email servers and encrypted mail setups
• Reliable, fast, and stable even with large inboxes

Privacy & Security

K-9 Mail is designed with transparency and privacy in mind.
• No ads
• No analytics
• No third-party trackers

With OpenPGP support through OpenKeychain, you can easily encrypt, decrypt, sign, and verify emails — ensuring your communication stays private and secure.

Your emails stay between you and your provider, not harvested or analyzed by the app.