Attach a verified stamp to any email you send. Anyone can check it's authentic — no app or account needed.
What your recipient sees when you stamp an email
Connect your Gmail account in one click. Your email address is automatically verified — no confirmation code needed.
Click once in Gmail. We run a quick human check to keep stamps trustworthy, then generate your badge.
Your recipient sees a badge in the email and can verify it's genuinely from you — right in their browser.
A note on what this is (and isn't). signedinbox makes it meaningfully harder for bots and impersonators to fake your identity, and adds a genuine signal of care and sincerity to your emails. It is not an absolute guarantee — determined attackers have workarounds for most verification systems. Think of it like a wax seal on an envelope: it doesn't make the letter invulnerable, but breaking it is obvious, and that matters.
Your email content stays on your device. We never see recipient addresses, subject lines, or email body text. Everything is hashed locally in your browser before anything reaches our servers. Read our full privacy policy →
Takes two minutes to set up.