Tyr

Peer-to-peer email on the Yggdrasil network.

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Screenshots

What is Tyr?

Tyr runs a complete mail server on your Android device and routes mail over the Yggdrasil mesh network — no central mail servers, no port forwarding, no STUN/TURN. Messages route directly between nodes, and Yggdrasil encrypts everything in transit.

Your address is derived from an Ed25519 public key (<64-hex>@yggmail), so it cannot be spoofed. Standard SMTP/IMAP is exposed on localhost, so any mail client works; DeltaChat/ArcaneChat give the best P2P messaging experience.

Features

• Built-in P2P chat (text + photos) over Yggdrasil — no third-party app required
• DeltaChat / ArcaneChat auto-configuration
• Works with any SMTP/IMAP client (K-9 Mail, Thunderbird Mobile, FairEmail)
• Local SMTP (127.0.0.1:1025) and IMAP (127.0.0.1:1143) servers
• Ed25519 cryptographic identity
• Configurable Yggdrasil peers with RTT-based auto-discovery
• Push notifications with Doze-aware battery optimization
• Auto-start on boot
• Password-protected encrypted backup/restore
• Log collection with period selection and archiving

How it works

graph LR
    A[Tyr Chat] -->|built-in| B[Tyr service]
    C[DeltaChat/ArcaneChat] -->|SMTP/IMAP| B
    B -->|YMP| D[Yggdrasil network]
    D -->|P2P encrypted| E[Recipient's Tyr]

The mail server is yggmail-ng (Rust), embedded as a native library via UniFFI (libyggmail_mobile.so) and run as a foreground service. On top of Yggdrasil it exposes SMTP and IMAP4rev1 on localhost; any client can connect.

Built-in chat (since 1.8) uses the same encrypted P2P transport: text and photos, delivery/read receipts, tap-to-copy, auto-read on open, and suppressed notifications while a conversation is in the foreground.

Quick start

DeltaChat / ArcaneChat (recommended)

Automatic: complete onboarding (password + peers), start the service, install DeltaChat or ArcaneChat, then tap Setup DeltaChat/ArcaneChat — Tyr opens the app pre-configured.

Manual: create a new profile → Use a different server → enter your @yggmail address (from Tyr's main screen) and the password you set in Tyr.

Other clients (K-9 Mail, Thunderbird, FairEmail)

• Email: your <64-hex>@yggmail address
• Password: the password set during onboarding
• IMAP: 127.0.0.1:1143 (no TLS) · SMTP: 127.0.0.1:1025 (no TLS)

Tyr must be running for mail to flow — enable auto-start in settings. Use the QR Code button to share your address.

Security

• Password stored via Android Keystore (AES-256-GCM), with automatic recovery for known Keystore issues on Samsung and other devices
• P2P traffic encrypted by Yggdrasil in transit
• SMTP/IMAP bound to localhost only
• Ed25519 identity — address cannot be spoofed
• Password-protected encrypted backups
• Push without third-party push services or metadata exposure

Building from source

Prerequisites

• JDK 17
• Android SDK — Platform 36, build-tools, min API 23 (Android Studio provides these)
• Android SDK/NDK path configured (local.properties or ANDROID_HOME)

Gradle is provided by the wrapper (./gradlew) — no separate install.

Build

git clone https://github.com/JB-SelfCompany/Tyr.git
cd Tyr
./gradlew assembleDebug      # debug APK → app/build/outputs/apk/debug/
./gradlew installDebug       # install to a connected device

Rebuilding the native library (optional)

The prebuilt libyggmail_mobile.so files live in app/src/main/jniLibs/<abi>/ and the UniFFI bindings in app/src/main/java/uniffi/yggmail_mobile/. To rebuild them from yggmail-ng you additionally need:

• Rust (stable) + Android targets: rustup target add aarch64-linux-android armv7-linux-androideabi x86_64-linux-android i686-linux-android
• cargo install cargo-ndk
• Android NDK with ANDROID_NDK_HOME set

cd Yggmail-ng && ./build-android.sh        # then copy the .so + bindings per the script's hint

Technical details

Related projects

• yggmail-ng — the mail server that powers Tyr
• Yggdrasil Network — the mesh network
• DeltaChat · ArcaneChat — recommended clients
• K-9 Mail · Thunderbird Mobile · FairEmail
• Mimir — P2P messenger on Yggdrasil (sister project)

License

App: GPLv3 (see LICENSE). The embedded yggmail-ng library is MPL-2.0.