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Outlook does not normally let you assign a separate password to an email, as you would to a ZIP file. Instead, you protect messages with Microsoft Purview Message Encryption, Do Not Forward, or certificate-based S/MIME encryption.
For most people sending confidential information to Gmail, Yahoo, Outlook.com, or another external address, Options > Encrypt is the simplest choice. Use Do Not Forward when you also want to restrict forwarding and printing.
Choose the right Outlook protection method
| What you need | Use this Outlook feature |
|---|---|
| Keep an email and its contents confidential | Encrypt with Microsoft Purview Message Encryption |
| Restrict forwarding or printing | Do Not Forward or an IRM protection policy |
| Use certificate-based, end-to-end email encryption | S/MIME |
| Simply mark a message as sensitive | Sensitivity or a sensitivity label |
Choosing Confidential from Outlook’s sensitivity options does not password-protect the message. It is a classification or warning and does not, by itself, prevent forwarding, copying, or printing.
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Use this method when the Encrypt command is available in the new Outlook app.
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- Open Outlook and select New mail.
- Compose the message and add any attachments.
- On the message ribbon, select Options.
- Select Encrypt.
- Choose Encrypt or Do Not Forward.
- Finish the message and select Send.
Encrypt versus Do Not Forward
Encrypt protects the message and its attachments while the protection policy applies, but it does not automatically stop the recipient from forwarding or printing it.
Do Not Forward adds usage restrictions intended to prevent forwarding and printing. It is the better choice for information such as financial records, identity documents, internal reports, or confidential business correspondence.
These commands require a supported Microsoft account, subscription, and—particularly for work or school accounts—administrator configuration. If Encrypt is missing, your organization may not have enabled the necessary Microsoft 365 licensing or policy.
Encrypt an email in classic Outlook for Windows
- Start a new message.
- Select the Options tab.
- Select Encrypt.
- Choose Encrypt or Do Not Forward.
- Send the message.
Use the encryption control on the message-composing ribbon rather than relying on older instructions that say to use File > Encrypt. Microsoft has documented an issue in some classic Outlook builds where using File > Encrypt caused recipients to receive a message_v2.rpmsg attachment they could not open. Updating Office is the preferred fix; on an affected installation, use Options > Encrypt.
Encrypt an email in Outlook on the web
For a Microsoft Purview-protected message, open Outlook in your browser and follow the same general path:
- Select New mail.
- Compose the email.
- Select Options on the message toolbar.
- Select Encrypt.
- Choose Encrypt or Do Not Forward.
- Select Send.
Some Outlook on the web accounts expose S/MIME under More options > Message options. That is a different certificate-based system, described below.
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Encrypt an email in Outlook.com
Outlook.com users with an eligible Microsoft 365 Personal or Microsoft 365 Family subscription can use message-level encryption:
- Create a new message at Outlook.com.
- Select Options.
- Select Encrypt.
- Choose Encrypt or Do Not Forward.
- Send the message.
The No permission set option removes message-level protection. It does not disable ordinary transport security such as opportunistic TLS.
What happens to attachments?
Attachment behavior depends on the protection option and the recipient’s mail service.
- With Do Not Forward, Word, Excel, and PowerPoint files generally remain encrypted after download.
- PDF and image attachments may be downloadable without the same restrictions.
- With ordinary Encrypt, Outlook.com, new Outlook, and Outlook mobile may allow some recipients to download attachments in unencrypted form.
- Recipients using Gmail, Yahoo, or another external service may be directed to Microsoft’s secure message portal.
What the recipient sees
A recipient using Outlook or Microsoft 365 will often open the protected message normally and see a banner describing its encryption or restrictions.
An external recipient may receive a notification with a Read the message link. Depending on the recipient’s provider, they can authenticate with Google, Yahoo, or Microsoft, or request a one-time passcode. Microsoft’s one-time passcodes expire after 15 minutes.
If the protected email does not appear correctly in Outlook’s reading pane, the recipient should open it in a new window. Encrypted messages can have display problems when conversation view is enabled.
How to use S/MIME encryption in Outlook
S/MIME is appropriate when your organization requires digital certificates. It is not a convenient replacement for a password when sending a one-off message to someone who uses Gmail.
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S/MIME requires:
- A digital ID or S/MIME certificate for the sender.
- The recipient’s certificate for encryption.
- A compatible mail application and access to the corresponding private key.
For an external recipient, you generally need to obtain and install that person’s public certificate before Outlook can encrypt a message for them.
New Outlook or Outlook on the web: send one S/MIME message
- Start or open a message.
- Select More options > Message options.
- Select Encrypt this message (S/MIME).
- Select OK.
- Send the message.
Classic Outlook: enable S/MIME for every outgoing message
- Select File > Options > Trust Center.
- Select Trust Center Settings.
- Select Email Security.
- Under Encrypted email, enable Encrypt contents and attachments for outgoing messages.
- Select Settings if you need to choose a certificate.
- Select OK to save the setting.
This applies to new messages, replies, and forwards. Do not enable it casually: messages sent to recipients without the necessary certificates may fail to send or open.
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- Select Outlook > Accounts.
- Select the account you use to send mail.
- Select Security.
- Under Certificate, select your certificate.
- In a message, select See more items (…).
- Select S/MIME > Encrypt with S/MIME.
- Complete and send the message.
The recipient’s certificate encrypts the copy intended for that recipient. Your own certificate is used for the copy saved in Sent Items or Drafts.
Why the Encrypt button is missing
The command may be unavailable for several reasons:
- Your account or Microsoft 365 subscription does not include the required encryption feature.
- Your work or school administrator has not enabled Purview Message Encryption or IRM.
- You are using an Outlook account type or client that does not support the feature.
- Your organization has hidden or replaced the command with a sensitivity-label policy.
For a work account, contact your Microsoft 365 administrator. For a personal account, check that you are signed in with the eligible Microsoft 365 subscription account and that Outlook is updated.
Important limitations and failure cases
Do not combine Purview encryption and S/MIME
Microsoft advises against applying Purview or IRM protection to a message that is already S/MIME-signed or encrypted, and vice versa. Some clients, including Outlook for Mac, Outlook for iOS, and Outlook for Android, may not open messages protected by multiple encryption technologies.
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External Outlook users may see a blank message
An external recipient may be unable to open a Purview-protected message if their Outlook client cannot connect to the sender’s Azure Information Protection endpoint. External Conditional Access or multifactor-authentication rules, or a sensitivity label limited to internal recipients, can also cause this behavior. The sender’s Microsoft 365 administrator must usually correct the policy.
Shared mailbox access can be different
A user who accesses a shared mailbox through a security group may be unable to read an encrypted or restricted message sent to that mailbox, especially when Outlook automapping is not enabled. Microsoft documents two workarounds: use Open another mailbox in Outlook on the web, or grant full mailbox access directly to the user so automapping can be enabled.
Many individual recipients can trigger an error
Purview protection can fail with an error saying that too many users have been granted access. Microsoft attributes this to a 4 MB protection-policy limit. It commonly occurs when hundreds of individual addresses are entered. An organization-managed distribution group may avoid the problem if it is not expanded; a personal Outlook distribution list is treated as individual users and may not help.
When a separate password is genuinely required
If the recipient must enter a password that you choose, Outlook’s built-in encryption is not the exact tool. Put the sensitive file in an encrypted archive, such as a password-protected 7-Zip file, and send the password through a separate channel such as a phone call or messaging app. Do not send the archive and its password in the same email.
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Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.FAQ
Can I add a password directly to an Outlook email?
Not in the same way as a password-protected document or ZIP archive. Use Options > Encrypt, Do Not Forward, or S/MIME. If you need a password that you personally choose, send the content as a password-protected archive and share the password separately.
Does setting an email to Confidential protect it?
No. Outlook’s normal Confidential sensitivity setting communicates that the message is sensitive but does not itself encrypt the message or prevent forwarding, copying, or printing.
Can I send an encrypted Outlook email to Gmail?
Yes, when your account supports Microsoft Purview Message Encryption. The Gmail recipient may receive a Read the message link and authenticate or use a one-time passcode.
What is the difference between Encrypt and Do Not Forward?
Encrypt protects the message and attachments but does not automatically impose forwarding or printing restrictions. Do Not Forward adds restrictions intended to prevent those actions.
Why can my recipient not open the encrypted email?
Possible causes include an unsupported mail client, missing S/MIME certificates, restrictive Microsoft 365 policies, shared-mailbox permissions, or a client that cannot connect to the sender’s protection service. The sender’s Microsoft 365 administrator may need to investigate.
Does Outlook encryption protect PDF and image attachments?
Protection varies by encryption mode and client. Under Do Not Forward, Office files generally retain encryption after download, while PDFs and images may be downloadable without the same protection.
The Bottom Line
For most Outlook users, the practical solution is Options > Encrypt > Encrypt. Choose Do Not Forward when restricting forwarding and printing matters. Use S/MIME only when both sides have the required certificates and compatible software. If you need a user-created password, protect an attached archive instead—Outlook email encryption is policy-based, not a simple per-message password.
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