To automatically encrypt and/or digitally sign messages
  1. On the Tools menu, click Options.

  2. On the Security tab, select the appropriate check box(es).

  3. Click Advanced Settings.

  4. For encrypted messages, select an encryption algorithm. The message recipient must be using the same algorithm.

Tip
Related Topics

Sending an encrypted or digitally signed message

What are secure messages?

Adding a digital ID to the Address Book