How to Encrypt an Email in Outlook

If you are asking how do I encrypt an email in Outlook, the short answer is: open a new message, go to Options → Encrypt and pick Encrypt or Do Not Forward. That button uses Microsoft Purview Message Encryption and needs a qualifying Microsoft 365 plan. Without one, you can still encrypt with S/MIME, which relies on digital certificates rather than a subscription feature.

Which method works for you depends on your Outlook version, your account type and whether the person you are writing to can read the message. This guide covers each route, what the options actually do and the limits you should know before sending anything sensitive.

Which Encryption Options Does Outlook Offer?

Outlook offers two separate encryption systems: Microsoft Purview Message Encryption and S/MIME. They solve the same problem in different ways, and you should not apply both to the same message.

• Microsoft Purview Message Encryption (previously called Office 365 Message Encryption) protects the message inside Microsoft's cloud. Recipients on other email services read it through a secure web portal after signing in or entering a one-time passcode.
• S/MIME (Secure/Multipurpose Internet Mail Extensions) encrypts the message with certificates. A certificate is a digital ID issued by a trusted authority. Both you and the recipient need one, and you need the recipient's public certificate before you can encrypt to them.

The practical difference is the recipient. Purview works with almost any recipient because the portal handles the decryption. S/MIME only works when both sides have exchanged certificates, which is common inside organisations and rare between individuals.

Which Microsoft 365 Plans Include Email Encryption?

Microsoft Purview Message Encryption is included in Microsoft 365 Business Premium, Microsoft 365 E3 and E5, Office 365 E3 and E5, Office 365 A1, A3 and A5, and Office 365 G3 and G5. Each user who sends encrypted mail needs a licence.

Microsoft 365 Business Basic, Business Standard, Office 365 E1, F3 and Exchange Online Plan 1 or 2 can get the feature by adding Azure Information Protection Plan 1. Microsoft lists the full picture in its message encryption FAQ.

Home users are covered separately. Microsoft 365 Personal and Family subscribers can send encrypted messages from Outlook.com and new Outlook for Windows. If you are weighing up a household plan, our Microsoft 365 Family guide explains what the subscription includes and how sharing works.

A one-time-purchase copy of Outlook, such as Outlook 2024, does not include the Purview Encrypt service on its own, because that service runs in Microsoft's cloud and is tied to a subscription. S/MIME is a different matter: it depends on certificates, not on a Microsoft 365 plan feature.

How Do I Encrypt an Email in Classic Outlook for Windows?

In classic Outlook, you encrypt a single message from the Options tab of the message window. These steps apply to Outlook 2016, 2019, 2021, 2024 and the Microsoft 365 version when your account supports encryption.

1. Select New Email and add your recipients, subject and text.
2. Open the Options tab and select Encrypt.
3. Choose the restriction you need, such as Encrypt or Do Not Forward. If you use certificates, choose the S/MIME option instead.
4. Check the banner at the top of the message, which confirms the protection applied.
5. Select Send.

To encrypt every message you send with S/MIME, go to File → Options → Trust Center → Trust Center Settings → Email Security. Under Encrypted email, tick Encrypt contents and attachments for outgoing messages, select Settings to choose your certificate if needed, then select OK. Only do this if most of your contacts have certificates, or many messages will fail to send.

How Do I Encrypt an Email in New Outlook and Outlook.com?

In new Outlook for Windows and Outlook on the web, open the message's Options tab, select Encrypt, and choose a protection level. The layout differs from classic Outlook, so our new Outlook vs classic Outlook comparison is worth a look if you switch between them.

1. Select New mail and write your message.
2. Select Options → Encrypt.
3. Choose Encrypt or Do Not Forward.
4. Select Send.

For S/MIME in new Outlook, use Options → More Options and tick Encrypt this message (S/MIME). To apply it to every message, go to Settings → Mail → S/MIME and turn on Encrypt contents and attachment for all messages I send. New Outlook does not import certificates automatically, so you or your administrator must install them first. Microsoft's guide to sending S/MIME or Purview encrypted emails in Outlook covers certificate setup in more detail.

What Is the Difference Between Encrypt and Do Not Forward?

Encrypt keeps the message encrypted while letting the recipient forward it and, in many cases, download attachments. Do Not Forward adds restrictions: the recipient cannot forward or copy the message, and Word, Excel and PowerPoint attachments stay protected after download.

Do Not Forward has one gap worth knowing. Microsoft notes that PDFs and images attached to a Do Not Forward message download without encryption. If the attachment is the sensitive part, protect the file itself as well.

Neither option stops someone taking a photo of their screen. Encryption protects the message in transit and in storage; it does not control what a trusted recipient does after reading it.

Can You Password Protect an Email in Outlook?

Outlook has no setting that puts a password on an individual email. The closest options are Purview encryption, where some recipients enter a one-time passcode, and protecting the attachment with its own password.

For an Office attachment, open the file and go to File → Info → Protect Document → Encrypt with Password in Word (Excel and PowerPoint have the same option under Protect Workbook and Protect Presentation). Enter the password twice and save. Send the password through a different channel, such as a phone call or text message, never in the same email. Microsoft cannot recover a forgotten document password, so store it somewhere safe.

What Does the Recipient See?

What the recipient sees depends on their email provider. Outlook.com and Microsoft 365 users read and reply to Purview-encrypted mail as normal, without extra steps.

Gmail and Yahoo users can sign in with their Google or Yahoo account, or request a temporary passcode. People on other providers receive a message with a link to the encrypted message portal and get a one-time passcode by email. No separate download is required. If a passcode does not arrive, ask the recipient to check their junk folder before you resend.

A Common Mistake We See

The most common problem is assuming every copy of Outlook has the Encrypt button switched on. Someone installs a standalone Outlook licence, signs in with a free Outlook.com or IMAP account, and finds that the Purview options are missing or greyed out. Nothing is wrong with the installation. The cloud encryption service comes from the account's subscription, not from the desktop app.

The second mistake is stacking protection. Applying Purview encryption to a message already signed or encrypted with S/MIME can make it unreadable, so remove the S/MIME setting first. And if you wanted time to double-check a sensitive message, encryption is not the tool; our guide to delaying or scheduling an email in Outlook gives you that safety window, because recalling a message in Outlook only works in limited cases.

Frequently Asked Questions

How do I encrypt an email in Outlook for free?

There is no free version of the Purview Encrypt button; it comes with qualifying Microsoft 365 business, education or consumer plans. S/MIME does not need a Microsoft 365 plan feature, but you need a certificate, which may cost money depending on the issuer, and the recipient needs one too.

Why is the Encrypt button missing in Outlook?

The Encrypt button is usually missing because the account does not have a plan that includes Microsoft Purview Message Encryption, or because an administrator has not enabled it. Check which account you are sending from, since a personal IMAP or POP account will not show the Purview options.

Is encrypting email in Outlook the same as a secure email?

Mostly, yes. Outlook already sends mail over encrypted connections where the receiving server supports it, but that only protects the message in transit. Choosing Encrypt or Do Not Forward protects the message content itself, so only the intended recipients can open it.

Can a Gmail user read an encrypted Outlook email?

Yes. A Gmail user receives a message with a link to Microsoft's encrypted message portal. They can sign in with their Google account or request a one-time passcode, then read and reply in the browser. They do not need to install anything or create a Microsoft account.

Does S/MIME work in Outlook 2024?

Yes. Classic Outlook 2024 supports S/MIME encryption and digital signatures through File → Options → Trust Center. You need a certificate from a trusted issuer installed on your PC, and you need each recipient's public certificate before you can send them an encrypted message.

How do I encrypt email in Outlook on a phone?

Microsoft confirms that recipients can read encrypted messages in the Outlook mobile app. For sending, the most reliable approach is Outlook on the web or new Outlook for Windows, where the Encrypt option sits under the message's Options tab and works the same way across accounts.

Conclusion

To answer how do I encrypt an email in Outlook in one line: use Options → Encrypt if your Microsoft 365 plan includes it, or set up S/MIME certificates if it does not. Protect sensitive attachments separately and share passwords through a different channel. If you need a desktop copy of Outlook for your own PC, browse our Outlook licences, including Outlook 2024 Retail.

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