Encrypt e-mail messages

Sometimes you want additional protection for your e-mail communication to keep it from unwanted eyes. Encrypting an e-mail message in Microsoft Office Outlook 2007 protects the privacy of the message by converting it from (readable) plaintext into (scrambled) ciphertext. Only the recipient who has the private key that matches the public key used to encrypt the message can decipher the message for reading. Any recipient without the corresponding private key would see only garbled text.


  • This is a separate process from digitally signing a message.

  • Sending and viewing encrypted e-mail messages requires both sender and recipient to share their digital ID, or public key certificate. This means you and the recipient each must send the other a digitally signed message, which enables you to add the other person's certificate to your Contacts. Once both parties have shared certificates, sending and viewing encrypted e-mail messages between them is the same as with any other e-mail messages. You can learn about digital IDs here and learn how to get and exchange digital IDs here.

  • If you send an encrypted message to a recipient whose e-mail setup does not support encryption, Outlook notifies you and offers the option of sending the message in unencrypted format.

  • This process also encrypts any attachments sent with encrypted messages.

In this article

Encrypt a single message

Encrypt all outgoing messages

Encrypt a single message

  1. In the message, on the Message tab, in the Options group on the ribbon, click the Encrypt Message Contents and Attachments button Encrypt message and attachment .

    Note: If you don't see this button, click the Options Dialog Box Launcher in the lower right corner of the group to open the Message Options dialog box. Click the Security Settings button and in the Security Properties dialog box, select Encrypt message contents and attachments. Click OK and then close the Message Options dialog box.

  2. Compose your message and send it.

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Encrypt all outgoing messages

Choosing to encrypt all outgoing messages means, in effect, your e-mail is encrypted by default. You can write and send messages the same as with any other e-mail messages, but all potential recipients must have your digital ID to decode your messages.

  1. On the Tools menu, click Trust Center, and then click E-mail Security.

  2. Under Encrypted e-mail, 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.

  4. Click OK twice.

Note: 3DES is the default encryption algorithm used in Outlook 2007. For more information, see the Overview of certificates and cryptographic e-mail messaging in Outlook.

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