Using classic Outlook for Windows in business environments
If you would like to send an encrypted email in Outlook, please try the following:
- Open New Email in Outlook.
- On the Options tab, look for Encrypt.
- Select Encrypt and choose the desired protection option, then send the message.
If the Encrypt option is not available, it may indicate that Microsoft Purview Message Encryption is not enabled for your account, the required license is not assigned, or the feature is not configured by your Microsoft 365 administrator. Microsoft documents that a missing Encrypt button can occur due to licensing or configuration issues.
Please read here for more details. If you are the normal user, I recommend you to contact your IT admin and let them know your situation.