How to Send an Encrypted Proton Email to a Non-Proton User

Proton Mail's normal end-to-end encryption only covers the hop between two Proton addresses. Send to a Gmail or Outlook address the ordinary way and Proton has to decrypt the message to hand it to your recipient's provider, the same as any other email.

Password-protected email is the workaround: it wraps your message in a link that only opens with a password you set. The recipient doesn't need Proton, a plugin, or any setup on their end — just the password, which you send them a different way.

This matters for anyone sending something sensitive to a client, a lawyer, an accountant, or a family member who has never heard of Proton and never will. You get real encryption on your side without asking them to change anything on theirs.

Before you start#

You need a Proton Mail account — Free, Mail Plus, or any paid plan all include this feature, so there's no upgrade required just to send one protected message.

You need a way to get the password to your recipient that isn't the same email thread. A text message, a phone call, or a separate email works. Putting the password in the same message you're protecting defeats the point.

• A Proton Mail account (any plan, including Free)
• The recipient's email address — any provider works
• A separate channel to share the password (text, call, second email)

Password protection vs. PGP: which one applies to you#

Proton Mail actually offers two different ways to reach a non-Proton address with real encryption, and it's easy to conflate them. Password protection, covered in this guide, needs nothing from your recipient — just a password you share separately.

PGP is the other route, and it's built for a recipient who already manages their own encryption keys. If they send you a signed email with their public key attached, Proton shows a Trust key button; accept it and future messages between you encrypt automatically, no password or hint involved. You can also add their public key manually from their contact card under advanced PGP settings.

For a one-off message to someone who has never touched PGP, password protection is almost always the right tool — it asks nothing of them. Reach for PGP only when your recipient already runs their own key pair and the exchange is going to be ongoing.

How to send a password-protected email from Proton Mail#

1. 1

   Start a new message

   Open Proton Mail and click New message. Add your recipient's address as usual, even if it's a Gmail, Outlook, Yahoo, or any other non-Proton address.

2. 2

   Click the lock icon in the compose toolbar

   This is the External encryption option. It's separate from the padlock that shows automatic Proton-to-Proton encryption status — you're opening a dialog to set one manually.

3. 3

   Set a password

   Enter the password your recipient will use to open the message. Choose something you can relay easily by phone or text — this isn't your Proton account password and doesn't need to match any existing credential.

4. 4

   Add an optional hint

   The hint shows on the unlock page before the password is entered. Use it if there's any chance the recipient forgets or you want to avoid a second phone call — keep it vague enough that it's useless to anyone who intercepts the email but not the password itself.

5. 5

   Confirm and send

   Click Set encryption to save the password, finish your message, and send. The subject line and body are protected; only the recipient with the password can read the content.

6. 6

   Share the password separately

   Text it, call it in, or send it from a different email thread. This is the step that actually makes the feature secure — an intercepted email plus an intercepted password sent the same way is no protection at all.

What does the recipient see?#

Your recipient gets a notification email in their normal inbox — Gmail, Outlook, whatever they use — telling them they've received a password-protected message. It doesn't contain your actual content.

They click Unlock message, which opens a page in their browser. There, they enter the password you gave them separately and click Read message to view the email — no Proton account, download, or plugin required.

They can reply from that same page. Non-Proton recipients can reply to a password-protected email up to five times. One detail worth knowing before you rely on a back-and-forth: once they reply, your next reply to them is not end-to-end encrypted by default — you have to re-enable encryption on each reply in the thread, it doesn't carry forward automatically.

Platform differences: what changes by recipient provider#

What to do when it doesn't work#

Most reported problems are on the recipient's side, not Proton's, and they have straightforward fixes.

• Recipient says the notification never arrived: check their spam folder first, then confirm you typed the address correctly — a password-protected message to a mistyped address still sends, it just goes nowhere useful.
• Recipient can't get past the password screen: confirm you're both looking at the same password. It's case-sensitive, and a hint that's too vague sends people guessing at variations that all fail.
• The link says it's expired: password-protected messages expire 28 days after sending by default. If it's been longer than that, or you set a shorter custom expiry, the message is gone and you'll need to resend it.
• Recipient's IT department is blocking the link: this shows up most on corporate Outlook accounts with aggressive link-scanning. Ask them to check with IT about allow-listing mail from your domain, or send the password-protected message to a personal address instead.
• You need to change your mind after sending: Proton doesn't offer a one-click recall the way some corporate email systems do. Your realistic option is to edit the expiry date down from the compose confirmation if you catch it in time, or simply not share the password if you haven't already — the link is useless without it.

A faster way to keep this from being a manual step every time#

Setting a password, writing a hint, and then finding a second channel to share it works fine for one message to one person. It gets tedious fast if you're doing this regularly — a client who needs financial details every month, a recurring legal exchange, a vendor who's never going to set up Proton on their end.

AI Emaily connects to your existing mailboxes, including Proton via IMAP, and handles the repeatable parts of an inbox — drafting replies in your voice, filing messages by rule, and flagging what needs a human decision before anything sends. It won't replace Proton's password-protection dialog for a one-off sensitive message, but it removes the busywork around everything else in the thread so protecting the messages that actually need it doesn't get lost in the noise. Every AI-drafted reply needs your approval before it goes out — nothing sends on its own. We build AI Emaily.