Download Tundra.

macOS: Tundra is not yet notarized by Apple, so the first launch shows a Gatekeeper warning. Open System Settings → Privacy & Security and click Open Anyway. Every file on the releases page has a SHA-256 checksum and a minisign signature next to it.
Windows: The installer is not code-signed yet, so Windows may show a SmartScreen warning: choose More info, then Run anyway. Windows ships with every release and is newer to our testing than macOS and Linux, so tell us what you find at info@tundra-mail.com.
Linux: AppImage, .deb and .tar.gz for amd64 and arm64. Needs webkit2gtk 4.1, and a Secret Service keyring to store passwords. Tested by us on Linux with every release.
Signing in with Google: Google shows its unverified-app screen, because Tundra's Google verification is not complete, and Google caps unverified apps at 100 users. You can continue past the screen while there is room, or sign in through your own Google Cloud project; Tundra walks you through the six steps. On Google Workspace, create that project inside your organisation and set it to Internal: internal apps skip the unverified screen and the user cap. If your admin restricts third-party apps, they can allow it in the Admin console under API controls. Outlook and IMAP accounts have no such screen.
Where your data lives: ~/.tundra-mail on macOS, %LOCALAPPDATA%\Tundra Mail on Windows, ~/.local/share/tundra-mail on Linux. Delete the folder and the tundra-mail entries in your keychain, and Tundra forgets your mail, accounts and settings. A few display preferences stay in the system's web view storage.

Updates are checked at launch and every 4 hours, and install only when you click. Each update's signature is checked before it installs.

Read the install guide →

First ten minutes

Connect an account.
Open People and clear your noisiest sender.
Press ⌘K and ask when your next meeting is.
Press ? for the keys.

Verify a download

Every file on the releases page has a SHA-256 checksum and a minisign signature beside it. The public key is also printed here, so you are not trusting one page for both. Save the .sha256 and .minisig files for your build in the same folder as the app, then run:

untrusted comment: minisign public key 262EF72BA5D0A627
RWQnptClK/cuJpIqBhL5bqW1v+H5rd0xG8m9dHnAqIH8Uwu0mwyYOCEN

macOS, in Terminal

shasum -a 256 -c TundraMail-darwin-arm64.dmg.sha256
minisign -Vm TundraMail-darwin-arm64.dmg -P RWQnptClK/cuJpIqBhL5bqW1v+H5rd0xG8m9dHnAqIH8Uwu0mwyYOCEN

Windows, in PowerShell

Get-FileHash TundraMail-windows-amd64-setup.exe -Algorithm SHA256
Get-Content TundraMail-windows-amd64-setup.exe.sha256
minisign -Vm TundraMail-windows-amd64-setup.exe -P RWQnptClK/cuJpIqBhL5bqW1v+H5rd0xG8m9dHnAqIH8Uwu0mwyYOCEN

Linux

sha256sum -c TundraMail-linux-amd64.AppImage.sha256
minisign -Vm TundraMail-linux-amd64.AppImage -P RWQnptClK/cuJpIqBhL5bqW1v+H5rd0xG8m9dHnAqIH8Uwu0mwyYOCEN

Expect OK from the checksum (on Windows, the two hashes match) and “Signature and comment signature verified” from minisign. Tundra checks the same signature itself before it installs an update.