Certify your emails on the blockchain directly from Gmail — in one click.
Users
13
−4 in 30 days
Rating
0.0 / 5
unchanged in 30 days
Ratings
0
0 in 30 days
Store rank
#178K
#148K among extensions
Version
2.2.0
updated 13 Oct 2026
Users
monthly, 3 years
Latest, 17 Oct 2026:13 usersMove the mouse over the chart for any month
Ratings count
monthly, 3 years
Latest, 17 Oct 2026:0 ratingsMove the mouse over the chart for any month
The Chrome Web Store rounds user counts down to the leading digit, so the user line moves in steps. The ratings count is exact and is the better signal of real adoption.
About MailStone Gmail Extension
MailStone for Gmail lets you send two kinds of legally useful email without leaving Gmail: the Opposable Mail, a certified email with its evidence file, and the Electronic Registered Delivery (ERD), the electronic equivalent of a registered letter.
TWO PRODUCTS, ONE BUTTON
Click the MailStone button in the compose window and choose:
• Opposable Mail — your message reaches its recipients as usual; MailStone timestamps it, anchors it on the blockchain and keeps an evidence file of what you sent, to whom and when.
• Electronic Registered Delivery — your recipient is identified, then accepts or refuses the delivery; every step is timestamped and gathered in an evidence file, enforceable under eIDAS.
HOW IT WORKS
Opposable Mail
1. Compose an email in Gmail
2. Click MailStone, choose Opposable Mail and pick a MailStone folder
3. The extension adds the folder's address in Bcc
4. Send: your evidence file is built on MailStone servers
Electronic Registered Delivery
1. Compose an email and add your recipients in the To field
2. Click MailStone and choose Electronic Registered Delivery
3. Send as usual: a notification confirms that your delivery was taken into account
4. Follow its status (delivered, accepted, refused) from your MailStone space
WHY USE IT
✔ eIDAS-qualified timestamping and blockchain anchoring
✔ Up to 50 recipients in one registered delivery
✔ Your plan usage and registered-delivery credits shown in the extension
✔ Everything happens in Gmail: no copy-paste, no extra tool
PRIVACY
The extension never reads or stores the body of your emails. It keeps your MailStone account address and session in the browser to call the MailStone API. For a registered delivery, it reads the recipients of the message you are composing to prepare the delivery; Cc and Bcc recipients are flagged as not covered. Nothing is shared with third parties. Full policy: https://www.mailstone.io/terms