If you need to send an email containing a single personal identification number, you can use Microsoft 365 Message Encryption. (Note that this encryption is not approved for sensitive personal data, personal data meriting extra protection or confidential information.) Emails containing multiple personal identification numbers must not be sent with this encryption method; instead, they should be sent as an attached file encrypted with AES-Crypt.
For internal emails, the message will simply be marked as encrypted, and no additional steps are needed to open it if the recipient uses the web client at outlook.hb.se or Office 365. If the recipient uses Outlook 2016 to open the message, they will need to click a link, and the email will open in the web client.
For external emails, the recipient will need to click a link and request a one-time password to access the message.
Important:
S/MIME encryption should not be used. Only Microsoft 365 Message Encryption should be used (see the guide below). This encryption functionality is only available in the web client outlook.hb.se or if Office 365 is installed. The encryption feature is not available in Outlook 2016.
Encryption of emails in Outlook (external link)