Open-source mail for macOS, Windows, iOS and Android
j and k move through threads, e archives, ⌘K opens the command list. A Rust core keeps your recent mail on the device, so search, archive, star and move answer at once, even offline.
Flomsi prints the shortcut next to the action: in the toolbar, in the command palette, in the status line at the bottom. You pick the keys up by using the app, not by studying a cheat sheet.
Commands in one searchable list, each with its key beside it.
Hide a thread until later. When the time comes it returns to the top of the inbox, unread.
from:, to:, subject:, has:attachment, is:unread, is:starred, before:, after:, in:, account:. Full text over the mail on the device, and Search on the server for the rest.
Drag files onto the composer, open or save with one click, forward with the originals. Files that can run code are not opened from the mail.
Mail HTML is cleaned in the Rust core and drawn without a WebView or JavaScript. Trackers stay out until you click.
Gmail, iCloud, Yandex, Mail.ru, Fastmail or any IMAP server, with an app password. One inbox for all of them, or one account at a time.
On a phone the panes and the keys give way to a bar of buttons, swipes, and screens of their own for a conversation, a new message and settings. Touch targets are 48 points, and the theme follows the system.
Mailboxes, Search, Unread and Compose sit under your thumb. Tap the account line under the title to switch accounts or see them all.
Hold a message for its menu. Swipe right to archive, left to delete. Archive, delete and move wait five seconds with Undo before they reach the server.
Continue with Google or Microsoft on the provider's own page, or add any IMAP account with step-by-step app-password instructions. Microsoft sign-in comes later.
Two presets ship with the app. Each is a small JSON file in app/assets/keymaps, so changing a key is a one-line edit and a rebuild. The demo at the top follows the preset you pick here.
Reply, reply all and forward work in an open conversation: ↵ or o opens it. Single-key shortcuts only fire outside text fields, so typing an e in search types an e; it never archives the thread you were reading.
Archive, delete, star and move land in a local SQLite database first. An outbox replays them to the server two seconds later and survives a lost connection, so the list never waits on the network.
$ mailctl add-imap --email you@gmail.com \ --host imap.gmail.com \ --smtp-host smtp.gmail.com $ mailctl sync $ mailctl ls "is:unread" $ mailctl reply 12 --text "Works for me." $ mailctl save 345 1 --dir ~/Downloads
Continue with Google works in every download; 0.2.2 and 0.2.3 fix the return from the Google page on Android and behind some proxies. A new mark, an fl ligature whose l is the text cursor, on all four platforms and on this site. Android builds now use one permanent key.
Archive, delete and move wait five seconds with Undo before they reach the server. A conversation, a new message and settings each get a screen of their own.
A bottom bar with Mailboxes, Search, Unread and Compose, and dropdown menus for accounts and the rest. Swipe right to archive, left to delete, long press for everything else.
A start screen with Continue with Google, Sign in with Microsoft and Other email account. Sign-in happens on the provider's page and tokens refresh by themselves. Google sign-in is in the downloads from 0.2.1; Microsoft follows later.
On macOS, Windows and Android while Flomsi runs, one per conversation. On macOS, closing the window keeps mail coming in.
Load older mail at the end of the list brings 200 more messages. Search on the server looks past what is on the device.
Version 0.2.3, an early build. Here is what works and what comes next.
Version 0.2.3 · 24 Sep 2026
Builds for macOS, Windows, Android and iOS. They are not signed by Apple, Microsoft or Google yet: macOS, Windows and Android ask once before they open them, and on iOS you sign the app yourself with AltStore or Sideloadly.
macOS 12 or later on Apple silicon. Intel Macs: build from source for now.
Or in Terminal: xattr -dr com.apple.quarantine /Applications/Flomsi.app
64-bit Windows 10 or 11.
A 64-bit phone (arm64-v8a).
From 0.2.1 every release is signed with one permanent key, so updates install over the last version. 0.2.0 used a one-off key: uninstall it before installing 0.2.1, then add your accounts again.
iOS 15 or later.
Mail is checked when you open the app; there are no alerts while it is closed.
Continue with Google works from 0.2.3. Outlook, Hotmail and Microsoft 365 need Microsoft sign-in, which comes later; other providers use an app password.
Until Google has verified Flomsi, Google's page warns that the app is unverified: choose Advanced, then Go to Flomsi.
SHA256SUMS.txt covers every file. On Linux, sha256sum -c --ignore-missing SHA256SUMS.txt. On macOS, shasum -a 256 Flomsi-macOS.zip and compare with its line. On Windows, Get-FileHash Flomsi-windows.zip.
The terminal tool on the same core ships for Linux x86_64: mailctl-linux-x86_64, 10 MB. Run chmod +x on it first. It reads the password from $MAIL_PASSWORD or asks, and keeps it in a Secret Service keyring such as GNOME Keyring or KWallet, which a bare server may not run. It is built on Ubuntu 24.04 and needs a glibc at least that new.
On macOS, build it with make cli. On Windows, run cargo build --release -p mailctl in core/, and pass --data-dir %USERPROFILE%\.mail_ to open the app's mailbox. docs/SMOKE.md (in Russian) has a first check.
You need Rust (stable, through rustup) and Flutter, plus Xcode for macOS and iOS, or Visual Studio with the Desktop development with C++ workload for Windows. A build on your own Mac runs on Intel too: flutter build macos --release in app/ makes Flomsi.app. On Windows, run flutter build windows --release there.
Google and Microsoft sign-in appear only in builds given the app's client IDs, such as FLOMSI_GOOGLE_CLIENT_ID; docs/SETUP.md (in Russian) lists them. Without them, accounts use app passwords.
$ git clone https://github.com/zondaxxx/Flomsi $ cd Flomsi # run the macOS app from source $ make app-mac # the interface alone, with sample mail $ make app-mac-mock # mailctl, into core/target/release $ make cli