We're taught that email must go through servers. Why? Because the Internet was built around centralized infrastructure. Every email you send travels through multiple servers - your provider's server, maybe a few relay servers, and finally your recipient's provider's server. Each hop is a potential point of surveillance, censorship, or failure.

Even "encrypted" email solutions still rely on these centralized servers. They encrypt the message content but the metadata - who you're talking to, when, how often - is visible to anyone watching the servers.

But there is a network, called Yggdrasil, that gives everyone a free IPv6 and doesn't need a blessing from your ISP. We finally have this possibility to use true P2P email. And moreover, this network has strong encryption to protect all data that flows from one IP to another.

So, Tyr brings true peer-to-peer email to your Android device using these unusual conditions. Unlike traditional email clients, Tyr doesn't need:

Centralized mail servers (the connections are straight P2P)
Message encryption layers (the network takes care of that)
Port forwarding or STUN/TURN servers (Yggdrasil handles NAT traversal)

What does Tyr already have?

Full integration with DeltaChat - the best decentralized messenger
Local SMTP/IMAP server running on your device
Automatic Ed25519 key generation for your mail identity
Connection to the Yggdrasil Network with configurable peers
Auto-start on boot for always-on availability

One of Tyr's strong points is censorship circumvention: you can connect to any of hundreds of available Yggdrasil nodes, host your own, or even build a private network. Email freedom is literally in your hands.

How does it work?

Tyr runs a complete email server right on your Android device, using the Yggdrasil network for transport. The Yggmail mail server (built in Go) is embedded as a library inside the app and runs as a foreground service.

On top of Yggdrasil, it provides standard SMTP and IMAP protocols on localhost (127.0.0.1:1025 and 127.0.0.1:1143). Any email client can connect to these ports - but we recommend DeltaChat for the best P2P messaging experience.

Every Tyr installation generates unique Ed25519 cryptographic keys. Your mail address is derived from your public key, making it: <64-hex-characters>@yggmail. This means your identity is cryptographically verifiable and cannot be spoofed.

DeltaChat Integration

DeltaChat is the perfect companion for Tyr. It's a messenger that uses email protocols but provides a modern chat interface. When you configure DeltaChat to use Tyr's local server:

DeltaChat sends messages via SMTP to Tyr
Tyr wraps them in Yggmail protocol and sends through Yggdrasil
The recipient's Tyr receives the message via Yggdrasil
Their DeltaChat fetches it via IMAP from their local Tyr
All this happens peer-to-peer, with no central servers

Setting up DeltaChat with Tyr

Install Tyr and complete the onboarding (set password, configure peers)
Start the Yggmail service in Tyr
Copy your mail address from the main screen (looks like abc123...@yggmail)
Install DeltaChat from F-Droid or Google Play
In DeltaChat, choose "Advanced Setup"
Enter your Yggmail address and password
Configure servers manually:
- IMAP: Server 127.0.0.1, Port 1143, Security: None
- SMTP: Server 127.0.0.1, Port 1025, Security: None
Complete setup and start chatting!

Important: Tyr must be running for DeltaChat to send and receive messages. Enable auto-start in Tyr settings for seamless experience.

Building from source

Prerequisites

Android Studio (latest version recommended)
JDK 17
Android SDK (API 23-36)
Go 1.21+ and gomobile (only if rebuilding yggmail.aar)

Build steps

Clone the repository:

git clone <repository-url>
cd Tyr

Build debug APK:

./gradlew assembleDebug

Install to connected device:

./gradlew installDebug

APKs will be in app/build/outputs/apk/debug/ or app/build/outputs/apk/release/

Rebuilding yggmail.aar (optional)

If you need to rebuild the Yggmail library:

cd ../yggmail/mobile
# On Windows:
..\build-android.bat
# On Unix:
gomobile bind -target=android -androidapi 23 -javapkg=com.jbselfcompany.tyr -ldflags="-checklinkname=0" -o yggmail.aar .

Then copy yggmail.aar to Tyr/app/libs/

Technical details

Language: Kotlin 2.2.20
Min SDK: 23 (Android 6.0)
Target SDK: 33 (Android 13)
Architecture: Layered (UI → Service → Data)
Mail server: Yggmail (Go library, embedded via gomobile)
Network: Yggdrasil overlay network
Localization: English, Russian

Security Features

🔒 Security implementation:

Passwords are encrypted using Android Keystore System (AES256-GCM encryption)
Network encryption provided by Yggdrasil Network for all peer-to-peer communications
Local-only access: SMTP/IMAP ports (1025/1143) are bound to localhost only, not accessible from network
Cryptographic identity: Ed25519 keys ensure your mail address cannot be spoofed

Yggmail: The mail transfer agent that powers Tyr
Mimir: P2P messenger on Yggdrasil (sister project)
Yggdrasil Network: The mesh network infrastructure
DeltaChat: The recommended email-based messenger client

License

Tyr is open source software. The Yggmail library uses Mozilla Public License v. 2.0.

See LICENSE file for full details

README.md

Tyr

What is Tyr?