A sovereign mobile email & encrypted-chat client, written in pure Go.

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Vayu is Sanskrit for wind — the invisible carrier that moves things without being seen. VayuMail moves your mail the same way: no telemetry, no analytics, no vendor lock-in, no credential ever written to disk in plaintext. One language, one binary per platform.

VayuMail-Mobile is a sibling project to VayuPress and inherits its constitutional discipline: ten binding rules in GOVERNANCE-CONSTITUTION.md, mechanically enforced by CI on every push (scripts/constitution.sh). What is complete versus stubbed is always truthfully recorded in COMPLIANCE-TRACKER.md.

Why VayuMail

	VayuMail	Typical mail apps
Tracking pixels	Detected and flagged — "this sender tracks you"	Silently loaded
Remote content	Never fetched	Fetched by default
Credentials	AES-256-GCM sealed store / platform keystore	Often plaintext in a database
Onboarding	Type your email + app password — everything else auto-discovered (signed setup codes as fallback)	Type server settings by hand
Encryption	PGP built in; auto-encrypts when recipients have keys	Plugin or absent
Key discovery	Auto-fetches contacts' PGP keys from their server (WKD), on by default	Manual key exchange
Real-time mail	One held IMAP IDLE socket	Battery-hungry polling
Private chat	VayuTalk — ephemeral, E2E-encrypted, read-once; same relay as the web console	A separate messaging app & account
Telemetry	None. Verifiable — it's open source	"Anonymized analytics"
Server key pinning	Optional per-account SPKI pin	Not offered
App lock	PIN gate, idle auto-lock, offline brute-force throttle	Rare or subscription-gated
Sign out	One tap: connections closed, credentials wiped from the keystore, local data removed	Often leaves data behind
Multi-device settings	Encrypted blob in your own mailbox	Vendor cloud account

The five pillars

• Elegance — every element earns its place or is removed. One gradient accent, motion that runs only while something is moving (an idle screen renders zero frames), no chrome that does not do work.
• Minimalism — fewer UI elements than competitors, not more.
• Speed — SQLite on first paint, IMAP IDLE for instant delivery, virtualized lists, no spinner where a cached value exists.
• Intelligence — automatic threading, unified inbox, newsletter detection, one-tap unsubscribe, snooze, undo-send, full-text search with operators (from:, subject:, has:attachment, is:unread, before:, after:) — all computed on-device. The app learns nothing about you and sends nothing anywhere.
• Lightness — every dependency justifies its size; the binary-size budget is enforced in CI.

Security is the floor, not a pillar: credentials never touch disk in plaintext (platform keystore / AES-256-GCM sealed store), an optional PIN app lock with idle auto-lock and an offline brute-force throttle gates the whole UI (ADR-0010), and signing out wipes an account's credential from the keystore and its mail from the device.

Architecture

cmd/vayumail ──► ui (Gio, single-threaded event loop — never blocks)
                  │  eventCh (Event, buffered 256)  ▲
                  ▼  cmdCh   (Cmd,   buffered 64)   │
              internal/syncmanager ──► internal/mail (IMAP/SMTP/MIME/PGP)
                          │
                          ▼
              internal/store (modernc.org/sqlite, WAL, FTS5)

• internal/mail, internal/store, internal/syncmanager never import Gio — CI-enforced. The engine runs headless (vayumail-cli) and builds with CGO_ENABLED=0.
• Credentials live in the platform keystore or the sealed AES-256-GCM store; SQLite holds a keystore alias, never a secret.
• Full topology and data-flow walkthroughs: docs/ARCHITECTURE.md.

Getting the app

Android — every release on the Releases page carries two files:

• vayumail-<version>.apk — install directly on a device (sideload).
• vayumail-<version>.aab — upload to the Google Play Console (Play requires an App Bundle, not an APK).

Cut your own by pushing a v* tag or running the Release APK + AAB workflow (Actions → Run workflow); GitHub Actions builds, signs, and attaches both. Set the ANDROID_KEYSTORE_B64 / ANDROID_KEYSTORE_PASS repository secrets to sign with your own upload key for the Play Store; without them builds are test-signed — fine for sideloading the APK, but Play only accepts an AAB signed with your registered upload key.

Desktop — the same binary runs on Linux/macOS/Windows:

make build && ./dist/vayumail

Headless engine:

go run ./cmd/vayumail-cli --help

Direct connect, end to end

Type your email address and an app password — the app fetches your server's signed-over-HTTPS autoconfig document (/.well-known/vayumail/autoconfig.json, served by VayuPress and contract-tested in both repositories) and connects. PGP keys then auto-sync from the server's WKD directory as mail arrives.

Prefer a handed-out credential? Ed25519-signed setup codes run the same verified provisioning path (Rule 7: nothing from an unverified payload is ever used), and this repository ships the reference issuer:

echo "you@example.com:app-password" > users.txt
go run ./cmd/vayumail-provision -server mail.example.com -users users.txt
# fetch http://localhost:8448/code?user=you@example.com and paste it into the app

See docs/ADR-0003-qr-provisioning-protocol.md and docs/ADR-0009-retire-qr-scanning-direct-connect.md.

VayuTalk — ephemeral encrypted chat

Beyond mail, the app carries VayuTalk: real-time, PGP end-to-end-encrypted messaging that interoperates with the VayuPress web console over one shared relay — a message sent from the web appears on the phone and vice-versa. Each message is encrypted to the recipient's key, delivered over a held Server-Sent-Events stream, and read-once: it vanishes when revealed or when its short TTL (5 min – 1 h) elapses, and nothing is ever written to disk. Compare safety numbers — yours and your contact's, side by side — over a trusted channel to confirm no one is in the middle.

When your server advertises a dedicated, CDN-proxy-off talk.<domain> relay, the app discovers it automatically (confirming it is within your mail domain and answering as a live relay) and routes its chat stream there — so real-time delivery works even behind a CDN that would otherwise challenge a non-browser client. Otherwise it falls back to the mail domain, unchanged.

Development

make lint          # gofmt + vet + boundary + all 10 constitution rules
make race          # full test suite under the race detector
make fuzz          # fuzz the MIME parser (the attacker-facing surface)
make coverage      # engine coverage report
make android       # local APK (requires Android SDK/NDK)

Quality gates on every push: constitution compliance, gofmt, go vet, staticcheck, race-detector tests, parser fuzzing, goroutine-leak checks (goleak), binary-size budget, and the Gio-free engine boundary. All tests run offline against fixtures and an in-memory IMAP server — CI needs no credentials and makes no network calls.

Permissions (Android)

INTERNET · FOREGROUND_SERVICE · RECEIVE_BOOT_COMPLETED — and no others, each justified in docs/ADR-0005-android-permissions.md. (CAMERA was withdrawn at v2.0.0 with QR scanning — ADR-0009.) A manifest change without a new ADR fails review; forbidden permissions fail CI.

Governance

• GOVERNANCE-CONSTITUTION.md — the ten rules, v1.2
• docs/ARCHITECTURE.md — normative topology
• docs/README.md — the ADR index (ADR-0001 … ADR-0010, every architectural decision, recorded)
• COMPLIANCE-TRACKER.md — the honest ledger
• CONTRIBUTING.md — how changes land

License

Apache License 2.0 — see LICENSE.