Sendsei | AI Email Tone Checker for Gmail & Outlook

AI email tone checker for Gmail & Outlook. Catch risky tone, get a one-click rewrite, and send what you meant.

Sendsei is an AI email tone checker for Gmail and Outlook. It reads your draft before you send it and tells you how it will actually land. Sent is forever. Send wisely. Spelling was never the problem. The problem is the reply written at 11 p.m., the ask buried under three apologies, the joke that dies the moment it becomes text. Sendsei gives every email one last, wiser read. HOW IT WORKS 1. Write your email in Gmail or Outlook on the web, like always. 2. Click "Check before send." 3. Get one plain verdict in seconds: send it, soften it, or sleep on it. 4. Like the suggested rewrite? Apply it to your draft in one click, or copy it. WHAT THE TONE CHECK CATCHES - Tone: how the email comes across to a real person, not just whether it's grammatically correct. - Risk flags: the passive-aggressive phrase, the buried ask, the line that reads as hostile, with the exact words that cause it. - Subject lines: flags a vague subject and suggests a better one. - A suggested rewrite that keeps your point but loses the problem, with spelling, grammar and capitalization fixed along the way. ONE VERDICT, NOT TWENTY UNDERLINES It's not a grammar checker. Grammar tools underline every comma while you type. Sendsei stays quiet until you ask, then reads your email the way the person on the other end will. A TONE CHECKER FOR GMAIL AND OUTLOOK Gmail and Outlook on the web, including Microsoft 365 work and school accounts. New emails, replies and forwards. Quoted threads are left alone; Sendsei only checks what you wrote. WHITE BELT (free) Tone read, risk flags and a one-click rewrite on every email. 4 checks a day. No credit card. BLACK BELT ($10/month) Everything in White Belt, plus the full context form (tell Sendsei your intent, the relationship, your tone goal and the stakes) and an intent read that judges whether your draft actually does what you set out to do. 50 checks a day. WHO IT'S FOR Founders, managers giving hard feedback, sales and client-facing roles, job seekers, students emailing professors, and anyone who has ever reread a sent email and winced. PRIVACY When you click "Check before send," your draft is sent securely to Sendsei's servers and to the Anthropic API to generate the review. Sendsei never stores your drafts, and they are never used to train any model. Privacy policy: https://sendsei.org/privacy Questions: hello@sendsei.org Install the free email tone checker and find out how often you were about to regret one.