On-device summaries
Message and conversation summaries run entirely on your Mac — nothing gets sent to a server. Apple Intelligence handles it by default, and there's an optional local model pack you can download for better results on longer threads.
What still uses the network
The usual things: syncing mail, signing in, fetching attachments you haven't opened before, and downloading the optional model pack. All standard mail operations — none of them involve sending your email content to an AI service.
Local caching
Kestrel caches messages and attachments on your Mac, so most of the time it doesn't need to contact the server at all. That means faster reads and less of your data in transit. Drafts save locally first too, then sync in the background. Actions like archive or delete get queued and replayed when you're back online.
Tracker protection
Kestrel blocks known email trackers before they load. Tracking pixels, remote images from tracking domains, and hidden resources embedded in message HTML are all stripped out before you see the message.
Secure storage
Account passwords and tokens are stored in the macOS Keychain. Saved drafts are encrypted on disk. Nothing is stored in plaintext.
Encrypted connections only
All connections to mail servers use TLS — the app won't connect over plaintext. Message content is also cleaned up before it's displayed, so hidden scripts and malicious links embedded in emails can't run on your Mac.
No telemetry
Kestrel doesn't phone home. There's no analytics, no crash reporting, and no usage tracking. The only servers the app talks to are your mail servers and, if you install the enhanced model pack, the one-time download endpoint for that.
Optional enhanced model pack
The enhanced model pack is a one-time download that lives on your Mac. You choose whether to install it, and the app shows you clearly whether it's installed, downloading, or removed.
This may evolve
Kestrel Mail is in active development and some details may change before launch. The direction won't: keep your data local, be transparent about what uses the network, and never sell or share your information.