To secure an email in Outlook, the main ways include encrypting the message, adding a digital signature, and applying sensitivity or IRM labels for protection. Encryption makes the email content unreadable to anyone except the intended recipient by converting it to cipher text. Outlook supports different encryption methods like S/MIME (which requires both sender and recipient to have certificates) and Microsoft Purview Message Encryption (part of Microsoft 365 subscriptions), which can restrict actions such as forwarding or printing. Users can also send digitally signed emails to verify their identity. These security options depend on the type of email account and whether the user has a Microsoft 365 subscription. To encrypt a single email in Outlook:
- Compose a new email.
- Go to the Options tab.
- Select Encrypt.
- Choose the appropriate encryption or restriction, for example, "Encrypt" or "Do Not Forward."
- Send the email.
To encrypt all outgoing emails by default:
- Go to File > Options > Trust Center > Trust Center Settings.
- Select Email Security.
- Check "Encrypt contents and attachments for outgoing messages."
- Apply and save settings.
For digitally signing an email, a digital ID/certificate must be installed, and this can be set up in Outlook's Trust Center under Email Security. For those without an organizational Microsoft 365 subscription, options may be limited, but encryption and password-protected emails can still be sent using some methods. Summary:
- Use Outlook's Encrypt option under email Options.
- Use S/MIME with certificates for signing/encrypting.
- Microsoft Purview Message Encryption allows advanced restrictions.
- Default encrypt all messages via Trust Center settings.
- Requires a Microsoft 365 subscription for most features.
This guidance ensures email security including confidentiality, integrity, and restricted sharing in Outlook.