Emails quarantined by the Email Impersonation control or Email data protection aren't visible in the recipient's quarantine portal but the email is visible to Quarantine administrator.
Email Security.cloud
The Data protection option is not enabled in the User Quarantine page.
Services > Email Services > User Quarantine
The Data protection option under "Users can view quarantined messages in Email Quarantine interface and summary notifications for the following services" in the page "Services > Email Services > User Quarantine " must be enabled.
Please allow up to 1 hour for propagation and the User (non - admin) can view emails quarantined by data protection service.