Privacy Policy
Last updated 29 August 2026 · applies to this Kestrel instance at mailbox.regnier.me
Kestrel is a self-hosted mail and calendar client. This instance is operated by Mathieu Régnier. It has no advertising, no analytics, and no relationship with any data broker — the only data it holds is what it needs to show you your own mail, calendar and tasks.
What is stored
When you connect a mail, calendar, or AI account, Kestrel stores:
- Your account credentials (password or OAuth token), encrypted at rest.
- A cache of your mail and calendar data — messages, threads, folders, events, tasks — fetched from the IMAP, CalDAV, or OAuth-connected accounts you add, so the app can search and display it without re-fetching everything on every page load.
- Application data you create directly: filing rules, saved searches, templates, signatures, scheduling polls, and any PGP keys you import.
- Session and sign-in data needed to keep you logged in, including a two-factor secret if you enable it.
- A push notification device token, only if you register one.
Optional AI features
AI-assisted sorting, search, and the assistant panel are off unless you configure a provider yourself. If you point them at a local provider (Ollama), nothing leaves this server. If you configure a third-party provider (OpenAI, Anthropic, Gemini, DeepSeek, or an OpenAI-compatible endpoint), the message content needed to answer that specific request is sent to that provider under its own privacy policy — Kestrel does not otherwise share your mail with them.
What is not done with your data
- It is not sold, rented, or shared with advertisers.
- It is not used to train any model Kestrel operates.
- Nobody but you (and, if self-hosted for you by someone else, the operator of the server) can read it.
Retention and deletion
Cached mail and calendar data is kept for as long as the connected account stays linked. Removing an account from Settings deletes its cached data and stored credentials. Deleting your Kestrel account deletes everything tied to it. Backups, where the operator keeps them, age out on their own schedule.
Security
Connected-account credentials and OAuth tokens are encrypted at rest. Traffic to and from this server is served over TLS. Two-factor authentication is available and recommended.
Contact
Questions, or a request to export or delete your data: reach the operator at mregnier150481@gmail.com.