Kestrel is out: Mac email, one key at a time
I'm Anthony, an independent developer in France. I've written software for a living since 2010, and Kestrel is the email client I make for the Mac: every action in it is one key away. Version 1.0 came out on 30 October, and the changelog lists what has shipped since.
Keys first
Press E and a conversation is done: it leaves your inbox and stays in your account, under Done. Press H and it goes away until a time you type, like "8 am" or "3 days", and it can come back only if nobody has replied by then. C composes, ⌘ Enter sends, / searches, and Z takes back the last thing you did.
You don't need to learn them all at once. ⌘K opens Kestrel Command, which finds any action by name and shows its key, so next time you can skip the search. The first time you open the app, a practice inbox with made-up mail teaches the keys one at a time.
Your mail goes from your Mac to your provider
Kestrel is an app, not a mail service. Your Mac talks to Gmail, Outlook or your IMAP server directly, and no Kestrel server sees your mail. Kestrel's own server checks your free trial or license key and, if you let it, offers updates. Sign-ins, mail passwords and API keys stay in the macOS keychain.
Senders hide tiny images in mail to learn when you open it. Kestrel takes out the ones it finds before a message loads and shows how many it stopped beside the date. ⌘U leaves a mailing list the way the list asks, in the background, and takes the conversation out of your inbox.
The catch
Gmail needs a Google Cloud project of your own, and Outlook needs your own app in Microsoft Entra. Google and Microsoft only let an app in through one of those, and Kestrel doesn't come with either, so you create yours. Each is free: Google takes about five minutes and Microsoft a few. Your Mac then talks to them through yours, with no one else's project or server in between.
Proton Mail (through Proton Mail Bridge), Fastmail, iCloud Mail and any other IMAP account need none of this, and the IMAP guide covers them. To look around before you set anything up, click Explore the demo inbox on the first screen. It opens made-up mail and never sends anything.
The other limits, so you don't have to find them yourself:
- Kestrel is Mac only, on macOS 15 or later.
- Outlook and IMAP accounts have no calendar and keep recent mail only, such as the latest 400 in the inbox.
- Reminders and Send Later run on your Mac, so Kestrel has to be open when one is due. If it isn't, it catches up the next time you open it.
AI, if you want it
Kestrel AI writes and rewrites drafts, summarizes threads, answers questions about your mail and labels new mail. You choose what runs it. Apple Intelligence on macOS 26, or a model you run yourself with Ollama or LM Studio, keeps the text on your Mac. With your own key for Anthropic or another provider, the text a feature needs goes to that provider's API. Set up none of these and the AI features stay off, while everything else works.
Auto Labels is on by default, with a switch in Settings → Kestrel AI, and the AI guide says what goes where. AI apps such as Claude Code can search, triage and draft through Kestrel's MCP server, but they can't send.
What it costs
Kestrel is free for 30 days on each Mac, with no account and no card. After that, a license is $20 a year for up to three Macs, with every update included. When the trial ends nothing is charged: Kestrel stops at the license screen, and your mail stays on your Mac and with your provider. If you buy a license and change your mind, you get your money back within 14 days.
For comparison, on 29 October Superhuman's Starter plan cost $25 a member a month, billed yearly, and Mimestream cost $49.99 a year. Superhuman runs on Windows, iPhone and Android, which Kestrel doesn't, and with Mimestream you sign in with Google and skip the project. The comparison pages put Kestrel next to both, with a source for every fact about the other app and a list of reasons to pick it instead.
Tell me what breaks
I'd like to hear which keys feel wrong and what breaks. In the app, Help › Send Feedback… sends me a message with your Kestrel and macOS versions, and the support page has the same form.