ThreeStrands is a source-available, keyboard-first, local-first email client inspired by some of the best email clients available. It is designed for people who spend significant time in email and want to process important conversations quickly without losing follow-ups, context, or control of their data.
The core experience combines:
- instant keyboard navigation and a discoverable command palette;
- focused inbox triage, local full-text search, and optimistic actions;
- reliable archive, read, star, label, and eventual follow-up workflows;
- offline access backed by a local SQLite cache; and
- a privacy-conscious desktop architecture that connects directly to mail providers without requiring a ThreeStrands backend in the free, signed-out mode.
ThreeStrands connects Gmail and IMAP/SMTP accounts in a desktop application for macOS and Linux, including Proton Mail through Proton Mail Bridge. Sign-in credentials are kept in your operating system's keychain, your messages and search index stay on your computer, and actions you take offline are synced to your provider when you reconnect.
NOTE: Only the macOS app is frequently used/tested currently.
Download the latest installer from GitHub Releases:
- macOS: the
.dmgfor Apple Silicon (aarch64) or Intel (x64). - Linux (x86-64): a
.deb,.rpm, or.AppImagepackage.
Launch ThreeStrands and add a Gmail account with Google sign-in, or connect an IMAP/SMTP account in Settings → Mail Accounts.
Reading, triage, and correspondence are available for Gmail and IMAP/SMTP. Compose with rich text, snippets, formatted signatures, and attachments; undo or schedule sends, browse Sent, and reuse a sent message with Edit as New. Newsletter controls include unsubscribe, mute, and Split Inboxes, while local Trust checks explain suspicious senders, links, and attachments. See features, keyboard shortcuts, and known limitations.
Google Calendar connects separately from mail. Find Times offers available slots beside a conversation, using working-hour blocks and optional travel buffers. Optional AI assistance can interpret requests such as “next week”; calendar searches also work without AI. At Inbox zero, open tasks, Keep in Touch reminders, and today’s agenda give you a next step.
Contacts include profiles with linked addresses, groups, birthdays, Keep in Touch reminders, CSV/vCard import and export, explicit profile merging, and reversible recipient-suggestion suppression. See contact management for workflows, export limits, and sync behavior.
- Every common action is available from the keyboard.
- The interface responds immediately, including on unreliable connections.
- Users can see and control what is synchronized or sent to optional services.
- Provider-specific behavior is isolated behind a tested capability contract.
- The desktop client connects directly to mail providers and requires no project-operated backend. Optional, end-to-end encrypted cross-device sync replicates application-owned workflow data through storage the user chooses.
Cross-device sync is described in
docs/cross-device-sync.md. It never carries
mail, provider credentials, or AI keys.
To build ThreeStrands yourself or contribute, see DEVELOPERS.md.
ThreeStrands uses its own name, visual identity, product language, and implementation. It learns from established interaction patterns across the email category without copying proprietary code, assets, or trademarks.
Copyright © 2026 OpenArc LLC. ThreeStrands is source available under the PolyForm Perimeter License 1.0.1.
You can inspect, build, use, and modify the software for permitted purposes, including personal and internal business use. Copying and redistribution are allowed subject to the license's conditions, including keeping the license and required notices. Providing others with a competing product built from this software is prohibited, even if that product is free.
The source is available so you can inspect how ThreeStrands handles your mail and credentials. This is a source-available license with a noncompete restriction, rather than an open-source license. The full text in LICENSE controls; third-party dependencies remain subject to their own licenses. OpenArc LLC may offer separate licenses for uses outside these terms.