Additionally, emails encrypted by Outlook stay within the Microsoft 365 network to avoid the security risks of the recipient’s email provider.

Learn how to encrypt your email in Microsoft 365 for extra security and privacy. Stopping any third-party from being able to read your email ...

The entire message reads: Microsoft Outlook cannot sign or encrypt this message because there are no certificates which can be used to send from the email address [email-id].

Microsoft has shared a temporary fix for a known issue preventing Microsoft 365 customers from replying to encrypted emails using the Outlook Desktop client.