otegami
An offline-first, open-source mail client for iOS and macOS. Otegami
connects to Gmail, iCloud, Yahoo! Mail (including Yahoo! Mail JAPAN),
Outlook.com/Office365, and any other IMAP/SMTP account through a single
sync engine, stores everything locally in SQLite (GRDB) with full-text
search, translates and summarizes English mail on-device, and can
optionally run its own self-hosted push notification relay.
iOS 26+ / macOS 26+, a single SwiftUI codebase. 日本語版 README:
README_ja.md.
Status: in development, experimental. Read Status below
before trusting it with real mail.
(The screenshots use development fixture accounts, not real mail.)
What otegami focuses on
Ahead of the feature list, two things this app is built around:
- Multiple accounts in one inbox. Every supported account type runs
on the same sync engine and lands in one unified inbox, sorted by
date. Tap a chip to filter down to a single account, or use the
per-account digest view to see everything at once.
- On-device translation and summarization. English mail is
translated to Japanese and summarized on-device via Apple's Foundation
Models framework (replies can be translated back to English too). See
AI summary & translation below.
Supported accounts
- Gmail — OAuth2 (Authorization Code + PKCE)
- iCloud — app-specific password
- Yahoo! Mail / Yahoo! Mail JAPAN — a dedicated setup form with
host/port/security pre-filled
- Outlook.com / Office365 — Microsoft OAuth2 (Authorization Code +
PKCE)
- Exchange — preset on top of the generic IMAP form
- Any other IMAP/SMTP provider
Gmail and Outlook/Office365 each require you to register your own OAuth
Client ID (the button is simply disabled if it's not configured — every
other feature works fine without it). See
docs/oauth-setup.md.
Features
- Unified inbox: an "All" chip mixes every account's mail by date,
plus per-account filter chips. Account-color accents and per-mailbox /
unified unread badges. An "unread only" toggle. Tapping the header
title opens a menu that jumps straight to any cross-account view
(inbox, flagged, archive, all mail, sent, drafts, spam, trash). A
"Group by account" toggle switches to a digest view (one row per
account: color stripe, display name, unread/count badge, a preview of
the 2-3 most recent messages; tap to filter to that account, swipe for
bulk actions) — available on macOS too. Account colors are
auto-assigned or can be overridden from a fixed 8-color palette, and
sync to other devices via iCloud.
- Offline-first: message, thread, and flag changes land in local
SQLite first. The app works with no network and replays queued
operations (read/unread, delete, archive, send) automatically on
reconnect. Archive behavior is tuned per provider (Gmail just removes
the label; everyone else moves the message to an Archive mailbox).
- Avatars: per-sender avatars, resolved in order from device contact
photos, external image sources, sender-domain logos, then initials.
Sources that make network requests can be disabled individually in
Settings → "Message List".
- Full-text search: SQLite FTS5 for queries of 3+ characters (shorter
queries fall back to
LIKE). Supports from:/to:/cc:/subject:
search operators, account filter chips, recent search history, and
saved searches (a search screen with History/Saved tabs).
- Threading: Gmail uses
X-GM-THRID; everyone else uses
References/In-Reply-To JWZ-style union-find plus a subject
fallback. The message view is an accordion (every message in the
thread listed chronologically, only the latest expanded, tap a header
to expand a different one) shared by iOS and macOS. The list shows a
count badge on multi-message threads.
- Collapsible quote history: plain-text replies break quoted
history into individual per-message cards, toggleable with "Show/hide
history" (shown by default; HTML mail is out of scope).
- AI summary & translation: see below.
- HTML mail: rendered in a sandboxed
WKWebView (JavaScript
disabled). Fixed-width marketing/notification tables are scaled to fit
the screen, with a one-tap "HTML" badge to switch to plain text.
Embedded images are off by default, remote images on by default, both
overridable per-message with a "Show images" banner. In-body links can
open in an in-app browser (default, iOS only) or the system default
browser.
Design
The UI is a from-scratch design: flat, zero corner radius, 2pt borders,
Archivo for Latin text / system font for Japanese, a pale-blue-tinted
light theme with a matching dark theme. See
docs/design-system.md for the adopted
information architecture and how design tokens are used.
- iOS (compact width, iPhone): a single persistent screen — unified
inbox, account filter chips, and an unread-only toggle. Tapping the
header title switches between cross-account views (inbox, flagged,
archive, all mail, sent, drafts, spam, trash); the top-left hamburger
menu (drawer) holds each account's mailbox tree plus Drafts, Outbox,
and the Settings entry point; a floating search button opens Search;
and a fixed footer toolbar on the message screen handles
reply/forward/etc. There is no bottom tab bar.
- iOS (regular width, iPad, etc.): 2-pane — list on the left, detail
on the right (
MailScreenView's size-class branch).
- macOS: the classic 3-pane
NavigationSplitView.
AI summary & translation
Summarization and translation run on-device via Apple's Foundation
Models framework (LanguageModelSession) — iOS/macOS 26+, requires a
device with Apple Intelligence enabled. The related UI collapses
automatically on unsupported devices.
- AI summary: a one-tap, per-message summary structured as
Summary / What they want / Action items. Reply mail excludes quoted
history from the summary target, covering only the new body text. A
"summarize in more detail" option regenerates a longer version.
- Translation: a translate button on English mail (always tappable
once the body has loaded). Auto-translate is off by default; even when
enabled it only fires on high-confidence English mail. One tap returns
to the original while a translation is shown. Plain text can be
checked paragraph-by-paragraph against the original; HTML mail keeps
its tables/images/layout and translates only the text. Paragraph-level
caching means re-translating is instant.
Engine design, supported languages, and known limitations (calling
Foundation Models from an iOS Simulator .app process fails with
FoundationModels.LanguageModelError -1, while the same call from a
swift test process on the same machine succeeds — a
Simulator/toolchain limitation, not an app bug) are documented in
docs/translation.md.
Usage
For a walkthrough of adding accounts, using the viewer, search, and
settings, see docs/usage.md.
Status
This is a personal, AI-assisted side project developed while keeping the
automated test/verification suite (make test, the scripts/verify-*.sh
checkpoints) green. It hasn't been published on the App Store or used as
anyone's daily driver for an extended period yet. Some behavior (real
account sign-in, two-device iCloud account sync round-trips, etc.) can't
be fully exercised by simulator-based automated tests and needs
confirmation on real accounts/devices — known limitations for each
feature are documented in the relevant docs/*.md.
Getting started
brew install xcodegen # needed to generate the Xcode project
make mac # macOS app (debug build)
make ios # iOS Simulator build
make test # OtegamiKit unit tests
Requires Xcode (iOS 26 / macOS 26 SDK, Xcode 26+). Debug builds show up
as "Otegami-dev" so they're distinguishable from a release install on
the same device. For device builds,
Gmail/Outlook OAuth, the dev mail stack (Dovecot + Mailpit), and
screenshot-based screen verification via scripts/verify-screen.sh, see
docs/development-setup.md.
Testing / verification
make test # OtegamiKit unit tests (fast, no simulator)
scripts/verify-screen.sh <scenario> [output.png] # tap-free screenshots
scripts/verify-relay.sh # otegami-relay E2E check
See docs/verify.md for what each checkpoint covers and
known simulator instabilities, and .claude/skills/verify/SKILL.md for
the automated-verification approach used in this project.
Architecture
apps/Otegami/ — the SwiftUI app (iOS + macOS), XcodeGen
project.yml.packages/OtegamiKit/ — platform-independent core: OtegamiCore
(models, threading), MailTransport/MailTransportMailCore
(IMAP/SMTP, MailCore2 adapter), OtegamiStore (GRDB schema/queries/
FTS), SyncEngine (sync + offline operation queue),
GoogleOAuth/MicrosoftOAuth, PushRelayClient, OtegamiRelayAPI
(DTOs shared with the server), OtegamiTranslation/
OtegamiTranslationFoundationModels/TranslationEngine (the
on-device translation/summarization stack).server/otegami-relay-go/ — the push relay (Go).dev/mailstack/ — the Dovecot + Mailpit development stack.
For module dependency direction, sync engine design, and known pitfalls,
see docs/architecture.md; for how the MailCore2
dependency is vendored, see
docs/build-mailcore2.md; for performance
testing, see docs/performance.md.
Documentation
Usage & features
Development
Auth & distribution
Contributing
Issues and pull requests are welcome — bug reports, questions, and small
fixes especially. See CONTRIBUTING.md for dev
environment setup, how to run tests, and commit/PR conventions. Report
security vulnerabilities through SECURITY.md rather than
a public issue.
License
MIT — see LICENSE.
Third-party licenses
Otegami depends on several third-party open-source packages via Swift
Package Manager (GRDB.swift, a MailCore2 fork and its C dependencies),
and Go modules for the push relay, and bundles the Archivo font (SIL Open
Font License). See NOTICE for license and copyright notices, and
server/otegami-relay-go/go.mod for the
relay module list and versions.
