How to Encrypt email messages in Outlook?

Encrypting Email Options

S/MIME encryption – To use S/MIME encryption, the sender and recipient must have a mail application that supports the S/MIME standard. Outlook supports the S/MIME standard

Before you start this procedure, you must first have added a certificate to the keychain on your computer. Once you have your signing certificate set up on your computer, you’ll need to configure it in Outlook.

1. Under the File menu, select Options > Trust Center > Trust Center Settings.
2. In the left pane, select Email Security.
3. Under Encrypted email, choose Settings.
4. Under Certificates and Algorithms, click Choose and select the S/MIME certificate.
5. Choose OK
6. Finish composing your email and then choose Send.

Microsoft 365 Message Encryption (Information Rights Management)

To use Microsoft 365 Message Encryption, the sender must have Microsoft 365 Message Encryption, which is included in the Office 365 Enterprise E3 license.

• If you are a Microsoft 365 subscriber, here is what is new to you:
  In an email message, choose Options, select Encrypt and pick the encryption that has the restrictions you want to enforce, such as Encrypt-Only or Do Not Forward.

Note:  Microsoft 365 Message Encryption is part of the Office 365 Enterprise E3 license. Additionally, the Encrypt-Only feature (the option under the Encrypt button) is only enabled for subscribers (Microsoft 365 Apps for enterprise users) that also use Exchange Online.

• For Outlook 2019 and 2016,
  In an email message, select Options > Permissions and pick the encryption option that has the restrictions you’d like to enforce, such as Do Not Forward.

1. In message that you are composing, click File > Properties.
2. Click Security Settings, and then select the Encrypt message contents and attachments check box.
3. Compose your message, and then click Send.

When you choose to encrypt all outgoing messages by default, you can write and send messages the same as with any other messages, but all potential recipients must have your digital ID to decode or view your messages.

1. On the File tab. choose Options >Trust Center > Trust Center Settings.
2. On the Email Security tab, under Encrypted email, select the Encrypt contents and attachments for outgoing messages check box.
3. To change additional settings, such as choosing a specific certificate to use, click Settings.