How Dusk's AI works without sending your mail anywhere

Where your mail goes

What the AI does

Sorts every email as it arrives

Each new email lands in a split: Important, Needs reply, Waiting, Other, Newsletters or Screened. You also see a short reason, like "You moved mail from this sender here" or "Asks you to confirm Thursday".

Rules go first, and the model is only asked when they can't decide. Your own mail is never marked as needing a reply. Senders you've moved stay where you put them. Likely phishing (a stranger, urgent words, and a link to a different site) is set aside in Screened.

Sums up each email in one line

The summary replaces the usual preview text, so you can read the inbox without opening anything. Very short emails, like "Thanks, see you then", keep their own words. There's no point asking a model to shorten them.

Digests long threads

Open a thread and a box at the top says what it's about, what they asked you, and offers quick replies. The thread also shows whose turn it is: "Waiting on you" or "Waiting on Maya".

Writes replies in your style

Press Tab in an empty reply for up to three suggestions, shown as grey text until you keep one. Press ⌘J to say what you want ("yes, but Thursday instead"), then make it shorter, friendlier or more formal. Dusk learns your usual greeting, sign-off and length from your sent mail. Grey text is never sent until you keep it.

Answers questions about your mail

Ask "what did the landlord say about the deposit?" and it searches your mail on the Mac, reads the likely threads and answers in a few sentences, with links to the threads it used.

How summaries are kept honest

Small models can state things that aren't there. We check every summary and digest before you see it:

• A summary has to share most of its words with the email, and can't name a fact the email doesn't contain. If it fails, Dusk shows a line from the email itself instead.
• An "ask" that names a number or person the email doesn't mention is dropped.
• Newsletters, automated mail, calendar invitations and your own messages never get asks or suggested replies.
• Hidden preview text that marketing emails carry is stripped before the model reads anything.

What it needs

• macOS 26 or later.
• A Mac that supports Apple Intelligence, which means Apple silicon.
• Apple Intelligence turned on in System Settings.

Without those, Dusk still works. It sorts with rules alone: people you know go to Important, everything else to Other. The status at the bottom of the sidebar says which mode you're in: "Sorted on this Mac" or "Sorting with rules only".

The trade-offs

Being honest about this matters more than the pitch.

• It's a smaller model. It's good at sorting, one-line summaries and short replies. A large cloud model is better at long, open-ended writing.
• It reads the start of each email. For sorting, it reads the headers and the first part of the text. That's enough for almost all mail.
• It's slower on older Macs. About 0.9 seconds per email on an M3 Max. Sorting happens in the background, so you rarely wait on it.
• It will sometimes sort wrongly. Press V to move an email and Dusk remembers that sender. Press Z to undo.

Why we built it this way

Your inbox holds contracts, medical letters, bank statements and private conversations. A mail app shouldn't need to copy them to a server to be useful. Now that Macs ship with a capable model, it doesn't have to. It's also why Dusk can cost $49 once: there's no AI server bill to pass on every month.

Does Dusk use ChatGPT, Claude or Gemini?

No. Only Apple's on-device model. There's no account to set up and no API key.

Does Dusk use Apple's Private Cloud Compute?

No. Dusk uses only the model on your Mac.

Can I turn the AI off?

Yes. Settings has a switch for on-device AI, and separate ones for auto drafts and learning your writing style.

Does it work offline?

Yes, for mail that's already downloaded. Summaries, digests and drafts don't need the internet.