Check your account and organization settings.
Outlook supports S/MIME and Microsoft Purview Message Encryption. Availability depends on the account, licensing, and configuration. New Outlook supports message encryption with an eligible subscription; it is not limited to classic Outlook.
Choose the protection for your message.
When composing a message, use the encryption controls available in your Outlook version. Your organization may also expose protection through sensitivity labels. Ask your administrator which option applies to the information you are sending.
Understand the recipient experience.
How recipients open an encrypted message depends on their account and the protection method. Test your organization’s approved workflow before using it for an important exchange.
If the option is missing
Ask your administrator to check licensing and configuration. See Microsoft’s current Outlook encryption instructions for your specific version.
Encryption is one control; it does not by itself establish compliance or prevent every form of data disclosure.