mailpen writes and rewrites email in your own voice: your greeting, your sign-off, your sentence length, how formal you are. Never AI-sounding. You read it, you send it.
Try it here, no account needed. Nothing you type is stored. mailpen never sends email.
One API, many places. mailpen shows up next to the compose box you already use, and the result is always plain text you read before you send.
Gmail
Chrome extension · phase 3
Outlook
Add-in, task pane · phase 4
mailpen.app
Web app, compose page · now
Your own tools
REST API, streaming · now
01 / How it works
Paste ten sent emails. mailpen measures sentence length, paragraph shape, greeting, sign-off, list habit, how formal you are, and writes your style profile. Every line of it is editable.
Two lines on what the email should say, or paste the thread you are answering. Pick a length. Tone controls exist, but stay out of the way until you need them.
The draft streams in as plain text. Select a sentence to shorten, soften or fix it. Accept copies the text into your mail client. mailpen never sends.
02 / The lint
Hard rules in the prompt, a deterministic lint after every draft, and evals that fail on a single violation. Buzzwords, empty superlatives, em dashes and markdown never reach you.
What models write
Hi Sam, Great to hear from you! I'm thrilled that the quote resonates with you — it's not just a project, it's a partnership. Rest assured, we'll leverage our expertise to deliver a seamless, robust and scalable result, and we'd be delighted to delve into the details as early as Monday. To get started, could you send over the signed order form at your earliest convenience? If you have questions before Monday, just reply here. Best regards, Maya
What you write
Hi Sam, Thanks for the quick reply, and great to hear the quote works for you. Monday suits us well, so let's start then. Could you send back the signed order form when you get a chance? Then I'll block the time and get everything lined up. If anything is unclear, just let me know. Cheers, Maya
Same message. Your words.
03 / Your email
Briefs and drafts persist only when you switch storage on. Logs never contain email text.
Every model call goes out with data collection denied. Zero data retention on request.
The message you are answering is wrapped as reference material, never as instructions. Whatever it says, mailpen writes for you.
No mailbox access, no send button. Accept copies the text; you paste it and press send.
04 / Pricing
Prices follow at launch. The waitlist hears first.
Free
Your key
Bring your own OpenRouter key. Every feature, your own model bill.
Join the waitlistPro
Included credits
Credits on the best models, picked by evals on real email. No key to manage.
Join the waitlist05 / Good questions
No. It has no access to your mailbox and no send button. Accept copies the plain text; you paste it into Gmail, Outlook, Proton or wherever you write, and you press send.
Any language you write in, formal or informal. mailpen follows the language of the thread you are answering, and one click translates a draft into another.
From emails you paste in. The measurable parts, such as sentence length, greetings, sign-off and list habit, are computed. The rest is one model pass over your samples. You can edit every field, and each save is a version you can go back to.
The best available through OpenRouter, chosen by evals on a set of real emails. Free brings your own key. Pro includes credits.
Yes. mailpen is an API first: write and rewrite endpoints, JSON in and out, optional streaming, one bearer token.
Email only. No newsletter, one message when you can get in.
