How to Encrypt Email in Outlook?

Desktop Outlook (Microsoft 365), step by step

1. Click New Email.
2. On the Options tab, click Encrypt (sometimes under Permissions).
3. Choose:
   • Encrypt-Only — recipients can read and often reply/forward, but the message is encrypted in transit and at rest under your org's policy.
   • Do Not Forward — recipients typically can't forward, print, or copy, depending on IRM settings.
4. Address, write, and Send as usual.

Outlook on the web: New message → ⋯ or Options → Encrypt → same Encrypt-Only / Do Not Forward choices when your tenant provides them.

Outlook mobile: compose → the shield / encrypt control in the compose toolbar, if your organization has enabled it. Personal accounts may not show it.

Personal Outlook.com / consumer Microsoft accounts: full Encrypt-Only IRM is aimed at Microsoft 365 business and education tenants. A personal inbox can still use TLS (automatic for most modern mail) and, if you set it up, S/MIME certificates — but the big Encrypt button from work Outlook often isn't there on a free Outlook.com account.

S/MIME (the other encryption path): install a personal or company S/MIME certificate, then enable it under Trust Center / Mail → S/MIME. Both sender and recipient need compatible certificates. This is separate from Microsoft 365 Encrypt-Only.

Encrypting does not hide the subject line the same way in every setup, and it doesn't replace being careful about who you address. If the Encrypt button is missing, the account type or admin policy usually hasn't turned the feature on — that's an IT/tenant setting, not a hidden checkbox on the client alone.

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