Postal Gambit
Chess by email, the way postal chess used to work
Correspondence chess over your own email
Postal Gambit is a local-first desktop app that keeps your games, enforces the rules and turns each move into a ready-to-send email in whatever mail client you already use. Your games never touch the network: your email is the board between you and your friend.
Slow, thoughtful chess with a real person. One move a day is a fine pace.
The game list, the board and the move history, in the dark theme.
How a game flows
No importer, no matchmaking, no lobby. You and a friend, moving at your own pace, with your own email in between.
Make your move
Click your piece, click its square. The board enforces every rule of chess: legality, check, mate, stalemate and all the draw rules, including the fifty-move rule and threefold repetition.
Send the email
Postal Gambit writes the whole email for you: a short note, an ASCII board diagram and the game record. One button opens it as a draft in your own mail client; another copies it to your clipboard for webmail. You press send.
Import the reply
When the reply lands, click its one-click import link or paste the email text into the app. Even a bare move like Nf6 from an opponent without the app imports fine. The board updates and it is your move again.
The email is the protocol
Every message a game sends is readable by a human first and a program second. This is roughly what your opponent receives.
Postal Gambit: oliver (White) vs jane (Black) Move 1 (White): e4 Your move. a b c d e f g h 8 r n b q k b n r 8 7 p p p p p p p p 7 ... -----BEGIN POSTAL GAMBIT v1----- Action: move From: oliver@example.org [the complete game record] -----END POSTAL GAMBIT----- Import this move with one click: [Open this move in Postal Gambit]
The block carries the entire game state, so a lost email never corrupts a game. The wire format is versioned and documented in the repo.
What is included
Everything a long-running set of postal games needs, nothing a chess website has.
Full rules enforcement
Legality, check, mate, stalemate and every draw rule. Promotion, castling and en passant all handled. You cannot send an illegal move and neither can your opponent.
One-click import
Every outbound email carries a link that opens the app with the move prefilled, with the same validation as a paste. The move data travels in the link itself and is never uploaded anywhere.
Any number of games
The list shows whose move it is in each game, with full move history and a short game code matching the email subject, so a game and its thread line up at a glance. Multi-select for bulk resign, draw acceptance, delete or re-send, each confirmed before anything destructive happens.
Invitations, draws, resignation
Starting a game, offering a draw, accepting one and resigning all travel over the same email format, so the whole game happens in one thread. Accepting an invitation fills your opponent's reply address automatically from the message.
Dark and light themes
A calm dark theme and a classic light board, toggled from the View menu and remembered between runs.
Keyboard-first
The whole app drives from the keyboard, dialogs included: arrow keys everywhere, Enter and Space both activate and the board plays with the cursor keys. Where focus is always shows on the thing you can act on, so a control rings while a list marks the row you are on.
Private by construction
No accounts, no server and no telemetry. The test suite structurally forbids network imports everywhere except the one disclosed update-check module, so your games are plain JSON files in your home directory and nothing about you ever leaves it.
No machines
No engine, no analysis, no hints, ever. The product is chess between people; "no machines" is scope, not a missing feature.
Questions a chess player actually asks
Answered plainly. Where the answer is no, we say so.
Does my opponent need the app?
No. Every email is readable text. An opponent without the app can reply with a plain move like Nf6 and it imports fine; they just miss the conveniences.
What email account do I need?
Any account you already use. Postal Gambit never sends anything itself: it opens a pre-filled draft in your own mail client or copies the email to your clipboard and you press send.
What happens if an email gets lost?
Nothing is corrupted. Every email carries the entire game state, so the next one that arrives catches you up. If the two sides ever disagree, the divergence is detected and reported, never silently resolved.
Can it stop my opponent cheating?
No. Nothing can. Correspondence chess has always been played on trust. What Postal Gambit guarantees is that every move is legal; whether a human chose it is between you and your friend.
Where do my games live?
In plain JSON files under your home directory, one per game, portable and inspectable. Delete the folder and they are gone; copy it and they are backed up.
Is it really offline?
Your games and moves never touch the network: only your own mail client sends your email. The app makes exactly one outbound call of its own, checked rather than promised: an anonymous daily ask of GitHub releases for whether a newer version exists, with an update prompt you can download, skip or defer. The test suite forbids network code anywhere else in what you install, the setup program included; it also asserts that single exemption cannot widen.
Built to be trusted
A small app with a strict engineering bar, because a years-long game deserves software that will not lose it.
Tested to the last line
The core logic carries a 100% test-coverage gate, as does the part of the Windows setup program that touches your machine. The build fails if a single untested line lands.
Architecture that holds
A clean layered core whose boundaries are enforced by automated structural tests, including the rule that no network code can creep into anything you install, the setup program included.
A versioned wire format
The email format is specified, versioned and frozen once released, with conformance tests mirroring the spec section by section. Your games outlive any one version of the app.
Open and forkable
GPL-3.0 with the full source on GitHub. If it ever stalls, anyone can read it, fork it or carry it on. Your games are plain files either way.
A quiet promise
Some things Postal Gambit will not do, on purpose.
- No engines. Not optional, not later. Chess between people.
- No server. Your games live on your machine and travel in your email.
- No account. There is nothing to sign up for and nothing to be locked out of.
- No telemetry. Nothing about you or your games ever leaves your machine. The app's one outbound call is an anonymous daily ask of GitHub releases for whether a newer version exists; it carries nothing and downloads nothing without you choosing it.
Download Postal Gambit
Pick your platform and you have the newest release. Free and GPL-3.0; local-first, so your games and your email stay on your own machine.
Version 1.2.0Windows
Windows 10 or 11, 64-bit
Download for WindowsRun the setup: it installs per-user, so no administrator rights are needed. If Postal Gambit is already running it offers to close it for you. It shows you what it is doing while it works.
macOS
Apple Silicon (M1 or later)
Download for macOSOpen the DMG and drag Postal Gambit into Applications.
Linux
Any distribution with Flatpak
Download for LinuxInstall with flatpak install --user postal-gambit.flatpak.
What is new in this release · All releases · Source on GitHub
Supporting Postal Gambit
Postal Gambit is free and stays free. There is no paid tier, no licence key and no feature held back behind a donation. If it has replaced something you were paying for or simply saved you an afternoon, a contribution supports its maintenance and continued development. The same button sits at the foot of the app's own window; it hands the address to your browser, so the app itself still opens no connection.
Donate