Kestrel Mail On-device summaries
Message and conversation summaries run entirely on your Mac; the app sends nothing to a server. Apple Intelligence handles them out of the box, and an optional local model pack takes over once installed, with the biggest gains on long threads.
What still uses the network
Kestrel connects for mail sync, sign-in, and attachments that are not cached yet. It also makes these requests:
- Update checks: the app periodically checks kestrelmail.app for signed updates.
- Account setup: Kestrel may look up your provider's server settings, including through Mozilla's public autoconfig directory, which sees only your email domain.
- Unsubscribe: clicking Unsubscribe sends the request to the sender's unsubscribe service.
- Remote images: these are off by default. If you enable them, images load directly from the sender's servers.
- Model pack: this is a single download from our server, if you choose to install it.
None of these send your email content to us or to any AI service.
Local caching
Kestrel caches messages and attachments on your Mac. Opening cached mail does not require another server request. Drafts save locally first, then sync in the background. Kestrel queues actions such as archive and delete while you are offline and replays them after you reconnect.
Tracker protection
Kestrel blocks known email trackers by default before they load. It strips tracking pixels, images from tracking domains, and hidden resources embedded in message HTML before you see the message. The blocklist of several thousand known tracking domains ships with the app. Remote images are also off by default, which stops resources from domains outside the blocklist. Both settings are in Settings > Privacy.
Secure storage
Account passwords and tokens are stored in the macOS Keychain. Drafts, queued actions, and account settings are encrypted on disk with keys held in the Keychain. Cached messages and attachments are stored in a local database that stays on your Mac; enable FileVault to protect it at rest.
Encrypted connections only
All connections to mail servers use TLS. The app will not connect over plaintext. Kestrel sanitizes message content before display so embedded scripts cannot run and links cannot redirect through unsafe URL schemes.
No telemetry
There's no analytics, no crash reporting, and no usage tracking. Kestrel does not collect or send anything about how you use the app, and every connection it makes is listed above.
Optional enhanced model pack
Once installed, the enhanced model pack generates summaries on your Mac. It is most useful on long threads with several senders. Settings shows whether the pack is installed, downloading, or removed.
Before launch
Kestrel Mail is in active development, so some details may change before launch. We will continue to document every network connection and will not sell or share your data.